Ink film constructions

ABSTRACT

An ink film construction including: (a) a first printing substrate selected from the group consisting of an uncoated fibrous printing substrate, a commodity coated fibrous printing substrate, and a plastic printing substrate; and (b) an ink dot set contained within a square geometric projection projecting on the first printing substrate, the ink dot set containing at least 10 distinct ink dots, fixedly adhered to a surface of the first printing substrate, all the ink dots within the square geometric projection being counted as individual members of the set, each of the ink dots containing at least one colorant dispersed in an organic polymeric resin, each of the dots having an average thickness of less than 2,000 nm, and a diameter of 5 to 300 micrometers; each ink dot of the ink dots having a generally convex shape in which a deviation from convexity, (DC dot ), is defined by: DC dot =1−AA/CSA, AA being a calculated projected area of the dot, the area disposed generally parallel to the first fibrous printing substrate; and CSA being a surface area of a convex shape that minimally bounds a contour of the projected area; wherein a mean deviation from convexity (DC dotmean ) of the ink dot set is at most 0.05.

FIELD AND BACKGROUND OF THE DISCLOSURE

The present invention relates to ink film constructions and, moreparticularly, to ink dots adhered to printing substrates. In particular,the ink film constructions comprise continuous ink dots, which may byway of example be obtained by ink jetting technology.

Currently, lithographic printing is the process in most common use forproducing newspapers and magazines. Lithographic printing involves thepreparation of plates bearing the image to be printed, which plates aremounted on a plate cylinder. An ink image produced on the plate cylinderis transferred to an offset cylinder that carries a rubber blanket. Fromthe blanket, the image is applied to paper, card or another printingmedium, termed the substrate, which is fed between the offset cylinderand an impression cylinder. For a wide variety of well-known reasons,offset litho printing is suitable, and economically viable, only forlong print runs.

More recently, digital printing techniques have been developed thatallow a printing device to receive instructions directly from a computerwithout the need to prepare printing plates. Amongst these are colorlaser printers that use the xerographic process. Color laser printersusing dry toners are suitable for certain applications, but they do notproduce images of a quality acceptable for publications such asmagazines.

A process that is better suited for short run high quality digitalprinting is used in the HP-Indigo digital printing press. In thisprocess, an electrostatic image is produced on an electrically chargedimage-bearing cylinder by exposure to laser light. The electrostaticcharge attracts oil-based inks to form a color ink image on theimage-bearing cylinder. The ink image is then transferred by way of ablanket cylinder onto the substrate.

Various printing devices have also previously been proposed that use anindirect inkjet printing process, this being a process in which aninkjet print head is used to print an image onto the surface anintermediate transfer member, which is then used to transfer the imageonto a substrate. The intermediate transfer member may be a rigid drumor a flexible belt, also herein termed a blanket, guided over rollers.

Using an indirect printing technique overcomes many problems associatedwith inkjet printing directly onto the substrate. For example, inkjetprinting directly onto porous paper, or other fibrous material, resultsin poor image quality because of variation of the distance between theprint head and the surface of the substrate, and because of thesubstrate acting as a wick. Fibrous substrates, such as paper, generallyrequire specific coatings engineered to absorb the liquid ink in acontrolled fashion or to prevent its penetration below the surface ofthe substrate. Using specially coated substrates is, however, a costlyoption that is unsuitable for certain printing applications.Furthermore, the use of coated substrates creates its own problems inthat the surface of the substrate remains wet and additional costlysteps are needed to dry the ink so that it is not later smeared as thesubstrate is being handled, for example stacked or wound into a roll.Furthermore, excessive wetting of the substrate causes cockling andmakes printing on both sides of the substrate (also termed perfecting orduplex printing) difficult, if not impossible.

The use of an indirect technique, on the other hand, allows the distancebetween the image transfer surface and the inkjet print head to bemaintained constant, reduces wetting of the substrate as the ink can bedried on the image transfer surface before being applied to thesubstrate. Consequently, the final image quality of the ink film on thesubstrate is less affected by the physical properties of the substrate.

Various quality ink film constructions notwithstanding, it is believedthat there is a need for further improvements in ink film constructions,such as ink-jet printing constructions.

SUMMARY OF THE INVENTION

According to some teachings of the present invention there is providedan ink film construction including: (a) a printing substrate; and (b) aplurality of continuous ink films, fixedly adhered to a surface of theprinting substrate, the ink films containing at least one colorantdispersed in an organic polymeric resin; the ink films having a firstdynamic viscosity within a range of 10⁶ cP to 3·10⁸ cP for at least afirst temperature within a first range of 90° C. to 195° C., the inkfilms having a second dynamic viscosity of at least 8·10⁷ cP, for atleast a second temperature within a second range of 50° C. to 85° C.

According to another aspect of the present invention there is providedan ink dot construction including: (a) a first fibrous printingsubstrate selected from the group consisting of an uncoated fibrousprinting substrate and a commodity coated fibrous printing substrate;and (b) at least one continuous ink dot, fixedly adhered to a surface ofthe first printing substrate, the ink dot containing at least onecolorant dispersed in an organic polymeric resin, the ink dot coveringan area of the top surface; the ink dot fulfilling a structuralcondition wherein, with respect to a direction normal to the surfaceover all of the area, the ink dot is disposed entirely above the area,an average or characteristic thickness of the single ink dot being atmost 1,800 nm.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first fibrousprinting substrate selected from the group consisting of an uncoatedfibrous printing substrate and a commodity coated fibrous printingsubstrate; and (b) at least a first continuous ink dot, fixedly adheredto a first surface of the first printing substrate, the ink dotcontaining at least one colorant dispersed in an organic, polymericresin, the dot having an average thickness of less than 2,000 nm; thedot being generally disposed above a particular surface of the surface;a penetration of the dot beneath the particular surface, with respect toa direction normal to the first surface being less than 100 nm; the inkdot having a generally convex shape in which a deviation from convexity,(DC_(dot)), is defined by:DC _(dot)=1−AA/CSA,AA being a calculated projected area of the dot, the area disposedgenerally parallel to the first fibrous printing substrate; and CSAbeing a surface area of a convex shape that minimally bounds a contourof the projected area; the deviation from convexity (DC_(dot)) being atmost 0.03.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a printing substrate;and (b) at least one ink film, fixedly adhered to a top surface of theprinting substrate, the ink film having an upper film surface distal tothe top surface of the substrate, wherein a surface concentration ofnitrogen at the upper film surface exceeds a bulk concentration ofnitrogen within the film, the bulk concentration being measured at adepth of at least 30 nanometers, at least 50 nanometers, at least 100nanometers, at least 200 nanometers, or at least 300 nanometers belowthe upper film surface, and the ratio of the surface concentration tothe bulk concentration is at least 1.1 to 1.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a printing substrate;and (b) at least one ink film, fixedly adhered to a top surface of theprinting substrate, the ink film containing at least one colorantdispersed in an organic polymeric resin, the ink film having an upperfilm surface distal to the top surface of the substrate, wherein asurface concentration of nitrogen at the upper film surface exceeds abulk concentration of nitrogen within the film, the bulk concentrationbeing measured at a depth of at least 30 nanometers below the upper filmsurface, and wherein a ratio of the surface concentration to the bulkconcentration is at least 1.1 to 1.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first printingsubstrate selected from the group consisting of an uncoated fibrousprinting substrate, a commodity coated fibrous printing substrate, and aplastic printing substrate; and (b) an ink dot set contained within asquare geometric projection projecting on the first printing substrate,the ink dot set containing at least 10 distinct ink dots, fixedlyadhered to a surface of the first printing substrate, all the ink dotswithin the square geometric projection being counted as individualmembers of the set, each of the ink dots containing at least onecolorant dispersed in an organic polymeric resin, each of the dotshaving an average thickness of less than 2,000 nm, and a diameter of 5to 300 micrometers; each of the ink dots having a generally convex shapein which a deviation from convexity, (DC_(dot)), is defined by:DC _(dot)=1−AA/CSA,AA being a calculated projected area of the dot, the area disposedgenerally parallel to the first fibrous printing substrate; and CSAbeing a surface area of a convex shape that minimally bounds a contourof the projected area; a mean deviation from convexity (DC_(dotmean)) ofthe ink dot set being at most 0.05.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first printingsubstrate selected from the group consisting of an uncoated fibrousprinting substrate, a commodity coated fibrous printing substrate, and aplastic printing substrate; and (b) an ink dot set contained within asquare geometric projection projecting on the first printing substrate,the ink dot set containing at least 10 distinct ink dots, fixedlyadhered to a surface of the first printing substrate, all the ink dotswithin the square geometric projection being counted as individualmembers of the set, each of the ink dots containing at least onecolorant dispersed in an organic polymeric resin, each of the dotshaving an average thickness of less than 2,000 nm, and a diameter of 5to 300 micrometers; each of the ink dots having a deviation from asmooth circular shape, (DR_(dot)), represented by:DR _(dot) =[P ²/(4π·A)]−1,P being a measured or calculated perimeter of the ink dot; A being amaximal measured or calculated area contained by the perimeter; a meandeviation (DR_(dotmean)) of the ink dot set being at most 0.60.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first fibrousprinting substrate selected from the group consisting of an uncoatedfibrous printing substrate and a commodity coated fibrous printingsubstrate; and (b) at least a first ink dot, fixedly adhered to asurface of the first printing substrate, the ink dot containing at leastone colorant dispersed in an organic, polymeric resin, the dot having anaverage thickness of less than 2,000 nm, and a diameter of 5 to 300micrometers; the ink dot having a generally convex shape in which adeviation from convexity, (DC_(dot)), is defined by:DC _(dot)=1−AA/CSA,AA being a calculated projected area of the dot, the area disposedgenerally parallel to the first fibrous printing substrate; and CSAbeing a surface area of a convex shape that minimally bounds a contourof the projected area; the deviation from convexity (DC_(dot)) being atmost 0.05, for the uncoated substrate; the deviation from convexity(DC_(dot)) being at most 0.025, for the commodity coated substrate.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first fibrousprinting substrate selected from the group consisting of an uncoatedfibrous printing substrate and a commodity coated fibrous printingsubstrate; and (b) at least a first ink dot, fixedly adhered to asurface of the first printing substrate, the ink dot containing at leastone colorant dispersed in an organic, polymeric resin, the dot having anaverage thickness of less than 2,000 nm; the ink dot having a generallyconvex shape in which a deviation from convexity (DC_(dot)) is definedby:DC _(dot)=1−AA/CSA,AA being a calculated projected area of the dot, the area disposedgenerally parallel to the first fibrous printing substrate; and CSAbeing a surface area of a convex shape that minimally bounds a contourof the projected area; the deviation from convexity (DC_(dot)) being atmost 0.04; the ink film construction being further defined by:DC _(dot<K) ·RDC,K being a coefficient; RDC being a reference deviation from convexity ofa reference ink dot in a reference ink film construction including thereference ink film disposed on a fibrous reference substratesubstantially identical to the first fibrous printing substrate, thereference deviation defined by:RDC=1−AA _(ref) /CSA _(ref),AA_(ref) being a calculated projected area of the reference dot, thearea disposed generally parallel to the reference substrate; andCSA_(ref) being a surface area of a convex shape that minimally bounds acontour of the projected area of the reference dot, the coefficient (K)being at most 0.25.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first printingsubstrate selected from the group consisting of an uncoated fibrousprinting substrate, a commodity coated fibrous printing substrate, and aplastic printing substrate; and (b) an ink dot set contained within asquare geometric projection projecting on the first printing substrate,the ink dot set containing at least 10 distinct ink dots, fixedlyadhered to a surface of the first printing substrate, all the ink dotswithin the square geometric projection being counted as individualmembers of the set, each of the ink dots containing at least onecolorant dispersed in an organic polymeric resin, each of the dotshaving an average thickness of less than 2,000 nm, and a diameter of 5to 300 micrometers; each ink dot of the ink dots having a deviation froma smooth circular shape (DR_(dot)) represented by:DR _(dot) =[P ²/(4π·A)]−1,P being a measured or calculated perimeter of the ink dot; A being amaximal measured or calculated area contained by the perimeter; whereina mean deviation (DR_(dotmean)) of the ink dot set is at most 0.60.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first fibrousprinting substrate selected from the group consisting of an uncoatedfibrous printing substrate and a commodity coated fibrous printingsubstrate; and (b) at least a first ink dot, fixedly adhered to asurface of the first printing substrate, the ink dot containing at leastone colorant dispersed in an organic, polymeric resin, the dot having anaverage thickness of less than 2,000 nm; the ink dot having a deviationfrom a smooth circular shape (DR_(dot)), represented by:DR _(dot) =[P ²/(4π·A)]−1,P being a measured or calculated perimeter of the ink dot; A being amaximal measured or calculated area contained by the perimeter; thedeviation (DR_(dot)) for the uncoated fibrous printing substrate, beingat most 1.5, at most 1.25, at most 1.1, at most 1.0, at most 0.9, atmost 0.8, at most 0.7, at most 0.6, at most 0.5, at most 0.4, at most0.3, or at most 0.25; the deviation (DR_(dot)) for the commodity coatedfibrous printing substrate, being at most 0.5, at most 0.4, at most 0.3,at most 0.25, at most 0.2, at most 0.15, at most 0.10, at most 0.08, atmost 0.06, or at most 0.05.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a first fibrousprinting substrate selected from the group consisting of an uncoatedfibrous printing substrate and a commodity coated fibrous printingsubstrate; and (b) at least a first ink dot, fixedly adhered to asurface of the first printing substrate, the ink dot containing at leastone colorant dispersed in an organic, polymeric resin, the dot having anaverage thickness of less than 2,000 nm, the average thickness being atleast 50 nm, at least 100 nm, at least 150 nm, at least 175 nm, at least200 nm, at least 225 nm, or at least 250 nm; the ink dot having adeviation from a smooth circular shape (DR_(dot)) represented by:DR _(dot) =[P ²/(4π·A)]−1,P being a measured or calculated perimeter of the ink dot; A being amaximal measured or calculated area contained by the perimeter; thedeviation (DR_(dot)) being at most 0.5, at most 0.4, at most 0.35, atmost 0.3, or at most 0.25; the ink dot construction being furtherdefined by:DR _(dot) <K1·RDR,K1 being a coefficient; RDR being a reference deviation from roundnessof a reference ink dot in a reference ink film construction includingthe reference ink film disposed on a fibrous reference substratesubstantially identical to the first fibrous printing substrate, thereference deviation defined by:RDR=[P _(ref) ²/(4π·A _(ref))]−1,P_(ref) being a measured or calculated perimeter of the reference inkdot; A_(ref) being a maximal measured or calculated area contained byP_(ref); the coefficient (K1) being at most 0.25.

According to yet another aspect of the present invention there isprovided an ink film construction including: (a) a printing substrate;and (b) a plurality of continuous ink films, fixedly adhered to asurface of the printing substrate, the plurality of the films containinga plurality of colorants dispersed in at least one organic polymericresin, the ink films covering an area of the surface, the plurality offilms having an average thickness of at most 2,200 nm, at most 2,100 nm,at most 2,000 nm, at most 1,900 nm, at most 1,800 nm, at most 1,700 nm,at most 1600 nm, at most 1500 nm, or at most 1400 nm; wherein, withinthe area, the ink film construction exhibits a color gamut volume of atleast 425 kilo(ΔE)³, at least 440 kilo(ΔE)³, at least 460 kilo(ΔE)³, atleast 480 kilo(ΔE)³, or at least 500 kilo(ΔE)³.

According to still further features in the described preferredembodiments, the first dynamic viscosity is at most 25·10⁷ cP, at most20·10⁷ cP, at most 15·10⁷ cP, at most 12·10⁷ cP, at most 10·10⁷ cP, atmost 9·10⁷ cP, at most 8·10⁷ cP, or at most 7·10⁷ cP.

According to still further features in the described preferredembodiments, the first dynamic viscosity is within a range of 10⁶ cP to2.5·10⁸ cP, 10⁶ cP to 2.0·10⁸ cP, 10⁶ cP to 10⁸ cP, 3·10⁶ cP to 10⁸ cP,5·10⁶ cP to 3·10⁸ cP, 5·10⁶ cP to 3·10⁸ cP, 8·10⁶ cP to 3·10⁸ cP, 8·10⁶cP to 10⁸ cP, 10⁷ cP to 3·10⁸ cP, 10⁷ cP to 2·10⁸ cP, 10⁷ cP to 10⁸ cP,2·10⁷ cP to 3·10⁸ cP, 2·10⁷ cP to 2·10⁸ cP, or 2·10⁷ cP to 10⁸ cP.

According to still further features in the described preferredembodiments, the first dynamic viscosity is at least 2·10⁶ cP, at least4·10⁶ cP, at least 7·10⁶ cP, at least 10⁷ cP, at least 2.5·10⁷ cP, or atleast 4.10⁷ cP.

According to still further features in the described preferredembodiments, the second dynamic viscosity being at least 9·10⁷ cP, atleast 10⁸ cP, at least 1.2·10⁸ cP, at least 1.5·10⁸ cP, at least 2.0·10⁸cP, at least 2.5·10⁸ cP, at least 3.0·10⁸ cP, at least 3.5·10⁸ cP, atleast 4.0·10⁸ cP, at least 5.0·10⁸ cP, at least 7.5·10⁸ cP, at least 10⁹cP, at least 2·10⁹ cP, at least 4·10⁹ cP, or at least 6·10⁹ cP.

According to still further features in the described preferredembodiments, the ratio of the second dynamic viscosity, at 90° C., tothe first dynamic viscosity, at 60° C., is at least 1.2, at least 1.3,at least 1.5, at least 1.7, at least 2, at least 2.5, at least 3, atleast 4, at least 4.5, at least 5, at least 6, at least 7, or at least8.

According to still further features in the described preferredembodiments, this viscosity ratio is at most 30, at most 25, at most 20,at most 15, at most 12, or at most 10.

According to still further features in the described preferredembodiments, the ink films have a glass transition temperature (T_(g))of at most 50° C., at most 44° C., at most 42° C., at most 39° C., atmost 37° C., at most 35° C., at most 32° C., at most 30° C., or at most28° C.

According to still further features in the described preferredembodiments, the plurality of ink films contain at least onewater-soluble or water dispersible material.

According to still further features in the described preferredembodiments, the at least one water-soluble material includes an aqueousdispersant.

According to still further features in the described preferredembodiments, the ink films contain at least 30%, at least 40%, at least50%, at least 60%, or at least 70%, by weight, of the water-solublematerial or the water dispersible material.

According to still further features in the described preferredembodiments, the ink films contain at most 5%, at most 3%, at most 2%,at most 1%, or at most 0.5% inorganic filler particles (such as silicaor titania), by weight.

According to still further features in the described preferredembodiments, the ink films are laminated onto the surface of theprinting substrate.

According to still further features in the described preferredembodiments, the ink films contain at least 1.2%, at least 1.5%, atleast 2%, at least 3%, at least 4%, at least 6%, at least 8%, or atleast 10% of the colorant, by weight.

According to still further features in the described preferredembodiments, the ink films contain at least 5%, at least 7%, at least10%, at least 15%, at least 20%, at least 30%, at least 40%, at least50%, at least 60%, or at least 70% of the resin, by weight.

According to still further features in the described preferredembodiments, the colorant includes at least one pigment.

According to still further features in the described preferredembodiments, the weight ratio of the resin to the colorant within theplurality of ink films is at least 1:1, at least 1.25:1, at least 1.5:1,at least 1.75:1, at least 2:1, at least 2.5:1, at least 3:1, at least3.5:1, at least 4:1, at least 5:1, at least 7:1, or at least 10:1.

According to still further features in the described preferredembodiments, the solubility of the resin in water, at a temperaturewithin a temperature range of 20° C. to 60° C., and at a pH within a pHrange of 8.5 to 10, is at least 3%, at least 5%, at least 8%, at least12%, at least 18%, or at least 25%, by weight of dissolved resin toweight of solution.

According to still further features in the described preferredembodiments, the ink films fixedly adhered to the surface are adheredprimarily, or substantially solely, by a physical bond between each ofthe ink films and the surface.

According to still further features in the described preferredembodiments, the adherence of the ink films to the surface, issubstantially devoid of an ionic character.

According to still further features in the described preferredembodiments, the adherence of the ink films to the surface, issubstantially devoid of a chemical bonding character.

According to still further features in the described preferredembodiments, the ink dot has a glass transition temperature (T_(g)) ofat most 47° C., at most 40° C., at most 35° C., or at most 30° C.

According to still further features in the described preferredembodiments, the ink dot contains less than 2%, less than 1%, less than0.5%, or less than 0.1% of one or more charge directors, or issubstantially devoid of charge directors.

According to still further features in the described preferredembodiments, the ink dot contains less than 5%, less than 3%, less than2%, or less than 0.5% of one or more hydrocarbons or oils, or issubstantially devoid of such hydrocarbons or oils.

According to still further features in the described preferredembodiments, fibers of the fibrous printing substrate directly contactthe ink dot.

According to still further features in the described preferredembodiments, the commodity coated fibrous printing substrate contains acoating having less than 10%, less than 5%, less than 3%, or less than1%, by weight, of a water-absorbent polymer.

According to still further features in the described preferredembodiments, the first fibrous printing substrate is a paper.

According to still further features in the described preferredembodiments, the fibrous printing substrate is a paper selected from thegroup of papers consisting of bond paper, uncoated offset paper, coatedoffset paper, copy paper, groundwood paper, coated groundwood paper,freesheet paper, coated freesheet paper, and laser paper.

According to still further features in the described preferredembodiments, an average single ink-dot or ink film thickness is at most1,600 nm, at most 1,200 nm, at most 900 nm, at most 800 nm, at most 700nm, at most 650 nm, at most 600 nm, at most 500 nm, at most 450 nm, orat most 400 nm.

According to still further features in the described preferredembodiments, the average single ink-dot thickness is within a range of100-800 nm, 100-600 nm, 100-500 nm, 100-450 nm, 100-400 nm, 100-350 nm,100-300 nm, 200-450 nm, 200-400 nm, or 200-350 nm.

According to still further features in the described preferredembodiments, the average single ink-dot thickness is at least 50 nm, atleast 100 nm, at least 150 nm, at least 200 nm, at least 250 nm, atleast 300 nm, or at least 350 nm.

According to still further features in the described preferredembodiments, the ink dot is laminated onto the surface of the printingsubstrate.

According to still further features in the described preferredembodiments, the total concentration of the colorant and the resinwithin the ink dot is at least 7%, at least 10%, at least 15%, at least20%, at least 30%, at least 40%, at least 50%, at least 60%, at least70%, or at least 85%.

According to still further features in the described preferredembodiments, the ratio of the surface concentration of nitrogen at theupper surface of the film to the bulk concentration of nitrogen withinthe film is at least 1.2:1, at least 1.3:1, at least 1.5:1, at least1.75:1, at least 2:1, at least 3:1, or at least 5:1.ratio being at least1.2:1, at least 1.3:1, at least 1.5:1, at least 1.75:1, at least 2:1, atleast 3:1, or at least 5:1.

According to still further features in the described preferredembodiments, the atomic surface concentration ratio of nitrogen tocarbon (N/C) at the upper film surface to the atomic bulk concentrationratio of nitrogen to carbon (N/C) at the depth, is at least 1.1:1, atleast 1.2:1, at least 1.3:1, at least 1.5:1, at least 1.75:1, or atleast 2:1.

According to still further features in the described preferredembodiments, the ink film contains at least one colorant dispersed in anorganic polymeric resin.

According to still further features in the described preferredembodiments, the surface concentration of secondary amines, tertiaryamines, and/or an ammonium group at the upper film surface exceeds theirrespective bulk concentrations at a depth of at least 30 nanometersbelow the film surface.

According to still further features in the described preferredembodiments, the upper film surface contains at least one polyethyleneimine (PEI).

According to still further features in the described preferredembodiments, the upper film surface contains a secondary amineexhibiting an X-Ray Photoelectron Spectroscopy (XPS) peak at 402.0±0.4eV, 402.0±0.3 eV, or 402.0±0.2 eV.

According to still further features in the described preferredembodiments, the upper film surface exhibits an X-Ray PhotoelectronSpectroscopy (XPS) peak at 402.0±0.4 eV, 402.0±0.3 eV, or 402.0±0.2 eV.

According to still further features in the described preferredembodiments, the upper film surface contains a poly quaternium cationicguar.

According to still further features in the described preferredembodiments, the poly quaternium cationic guar includes at least one ofa guar hydroxypropyltrimonium chloride and a hydroxypropyl guarhydroxypropyltrimonium chloride.

According to still further features in the described preferredembodiments, the upper film surface contains a polymer having at leastone quaternary amine group.

According to still further features in the described preferredembodiments, the ammonium group includes a salt of a primary amine.

According to still further features in the described preferredembodiments, the salt includes, or consists of, an HCl salt.

According to still further features in the described preferredembodiments, the upper film surface contains a polymer or compoundselected from the group consisting of poly(diallyldimethylammoniumchloride), poly(4-vinylpyridine), polyallylamine, a vinylpyrrolidone-dimethylaminopropyl methacrylamide co-polymer, a vinylcaprolactam-dimethylaminopropyl methacryamide hydroxyethyl methacrylatecopolymer, a quaternized copolymer of vinyl pyrrolidone anddimethylaminoethyl methacrylate with diethyl sulfate.

According to still further features in the described preferredembodiments, the ink film has an average thickness of at most 5,000nanometers, at most 4,000 nanometers, at most 3,500 nanometers, at most3,000 nanometers, at most 2,500 nanometers, at most 2,000 nanometers, atmost 1,500 nanometers, at most 1,200 nanometers, at most 1,000nanometers, at most 800 nanometers, or at most 650 nanometers.

According to still further features in the described preferredembodiments, the ink film has an average thickness of at least 100nanometers, at least 150 nanometers, or at least 175 nanometers.

According to still further features in the described preferredembodiments, the mean deviation from convexity is at most 0.04, at most0.03, at most 0.025, at most 0.022, at most 0.02, at most 0.018, at most0.017, at most 0.016, at most 0.015, or at most 0.014.

According to still further features in the described preferredembodiments, the square geometric projection has a side length within arange of 0.5 mm to 15 mm.

According to still further features in the described preferredembodiments, the square geometric projection has a side length of about10 mm, 5 mm, 2 mm, 1 mm, 0.8 mm, or 0.6 mm.

According to still further features in the described preferredembodiments, the diameter of the inkjet dot is at least 7, at least 10,at least 12, at least 15, at least 18, or at least 20 micrometers.

According to still further features in the described preferredembodiments, the mean deviation from convexity is at most 0.013, at most0.012, at most 0.010, at most 0.009, or at most 0.008.

According to still further features in the described preferredembodiments, the mean deviation from convexity for plastic substrates isat most 0.013, at most 0.012, at most 0.010, at most 0.009, or at most0.008.

According to still further features in the described preferredembodiments, the plurality of ink dots exhibits, on the plastic printingsubstrate, an adhesive failure of at most 10%, or at most 5%, whensubjected to a standard tape test.

According to still further features in the described preferredembodiments, the plurality of ink dots is substantially free of adhesivefailure when subjected to a standard tape test.

According to still further features in the described preferredembodiments, the ink dot set has at least 20, at least 50, or at least200 of the distinct ink dots.

According to still further features in the described preferredembodiments, the DC_(dotmean) is at least 0.0005, at least 0.001, atleast 0.0015, at least 0.002, at least 0.0025, at least 0.003, at least0.004, at least 0.005, at least 0.006, at least 0.008, at least 0.010,at least 0.012, or at least 0.013.

According to still further features in the described preferredembodiments, the average thickness is within a range of 100-1,200 nm,200-1,200 nm, 200-1,000 nm, 100-800 nm, 100-600 nm, 100-500 nm, 100-450nm, 100-400 nm, 100-350 nm, 100-300 nm, 200-450 nm, 200-400 nm, or200-350 nm.

According to still further features in the described preferredembodiments, the average thickness being at most 1,800 nm, at most 1,500nm, at most 1,200 nm, at most 1,000 nm, at most 800 nm, at most 500 nm,at most 450 nm, or at most 400 nm.

According to still further features in the described preferredembodiments, the average thickness is at least 100 nm, at least 150 nm,at least 175 nanometers at least 200 nm, at least 250 nm, at least 300nm, or at least 350 nm.

According to still further features in the described preferredembodiments, the mean deviation from roundness (DR_(dotmean)) being atmost 0.60, at most 0.60, at most 0.50, at most 0.45, at most 0.40, atmost 0.35, at most 0.30, at most 0.25, or at most 0.20.

According to still further features in the described preferredembodiments, DC_(dot) is at most 0.04, at most 0.03, at most 0.025, atmost 0.022, at most 0.02, at most 0.018, at most 0.017, at most 0.016,at most 0.015, at most 0.014, at most 0.013, at most 0.012, at most0.011, or at most 0.010, for an uncoated substrate.

According to still further features in the described preferredembodiments, DC_(dot) is at least 0.0005, at least 0.001, at least0.0015, at least 0.002, at least 0.0025, at least 0.003, at least 0.004,at least 0.005, at least 0.006, or at least 0.008, for an uncoatedsubstrate.

According to still further features in the described preferredembodiments, DC_(dot) is at most 0.022, at most 0.02, at most 0.018, atmost 0.016, at most 0.014, at most 0.012, at most 0.010, at most 0.008,at most 0.006, at most 0.005, or at most 0.004, for a commodity coatedsubstrate.

According to still further features in the described preferredembodiments, DC_(dot) is at least 0.0005, at least 0.001, at least0.0015, at least 0.002, at least 0.0025, at least 0.003, or at least0.0035, for the commodity coated substrate.

According to still further features in the described preferredembodiments, the uncoated printing substrate is a coated or uncoatedoffset substrate.

According to still further features in the described preferredembodiments, the fibrous printing substrate is a commodity-coatedprinting substrate.

According to still further features in the described preferredembodiments, the color gamut volume exhibited by the ink filmconstruction is at least 520 kilo(ΔE)³, at least 540 kilo(ΔE)³, at least560 kilo(ΔE)³, or at least 580 kilo(ΔE)³.

According to still further features in the described preferredembodiments, the plurality of continuous ink films have a plurality ofsingle ink dots, disposed above an area of the substrate, the ink dotshaving an average thickness of at most 900 nanometers, at most 800nanometers, at most 700 nanometers, at most 650 nanometers, at most 600nanometers, at most 550 nanometers, or at most 500 nanometers.

According to still further features in the described preferredembodiments, the plurality of continuous ink films includes a pluralityof single ink dots having a first thickness disposed above the area anda second thickness disposed below the area, within the substrate, atotal of the first thickness and the second thickness being at most 900nanometers, at most 800 nanometers, at most 700 nanometers, or at most600 nanometers.

According to still further features in the described preferredembodiments, the first thickness, or the total thickness, is at most 0.8micrometers, at most 0.7 micrometers, at most 0.65 micrometers, at most0.6 micrometers, at most 0.55 micrometers, at most 0.5 micrometers, atmost 0.45 micrometers, or at most 0.4 micrometers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, withreference to the accompanying drawings, in which:

FIG. 1A shows a top view of a magnified image of a plurality of inkjetink drops disposed on a paper substrate, according to an inkjet printingtechnology of the prior art;

FIG. 1B shows a top view of a magnified image of a plurality of inkjetink films disposed on a paper substrate, according to the inkjetprinting technology of the present invention;

FIGS. 2A-2C display three-dimensional laser-microscope acquiredmagnified images of ink splotches or films on paper substrates, obtainedusing various printing technologies, wherein: FIG. 2A is a magnifiedimage of an offset splotch; FIG. 2B is a magnified image of a liquidelectro-photography splotch (LEP); and FIG. 2C is a magnified image ofan inventive inkjet ink film construction;

FIG. 2D shows a two-dimensional shape having the mathematical propertyof a convex set;

FIG. 2E shows a two-dimensional shape having the mathematical propertyof a non-convex set;

FIG. 2F is a schematic top projection of an ink film having a rivuletand an inlet, the schematic projection showing a smoothed projection ofthe ink image;

FIGS. 3A, 3B, and 3C show surface roughness and surface heightmeasurements for the offset ink splotch construction, the LEP inksplotch construction, and the inventive inkjet ink film constructionprovided in FIGS. 2A-2C;

FIGS. 3D and 3E provide respective schematic cross-sectional views of aninventive ink film construction and an inkjet ink dot construction ofthe prior art, wherein the substrate is a fibrous paper substrate;

FIG. 3F provides a graph plotting the atomic concentration of copperwithin the ink dot and within the fibrous paper substrate, as a functionof depth, within a first cyan-colored inkjet ink film construction ofthe prior art;

FIG. 3G provides a graph plotting the atomic concentration of copperwithin the ink dot and within the fibrous paper substrate, as a functionof depth, within a second cyan-colored inkjet ink film construction ofthe prior art;

FIG. 3H provides a graph plotting the atomic concentration of copperwithin the ink dot and within the fibrous paper substrate, as a functionof depth, within a cyan-colored ink film construction of the presentinvention;

FIGS. 4A and 4C each show an image of the surface of the outer layer ofan intermediate transfer member; FIGS. 4B and 4D are correspondingimages of the surface of the ink films produced using those outerlayers, in accordance with the present invention;

FIG. 5A provides images of ink splotches or films obtained using variousprinting technologies on coated paper, along with correspondingimage-processor computed contours and convexity projections thereof;

FIG. 5B provides images of ink splotches or films obtained using variousprinting technologies on uncoated paper, along with correspondingimage-processor computed contours and convexity projections thereof;

FIG. 5C provides bar graphs of the deviation from roundness for ink dotson each of 19 fibrous substrates, according to some embodiments of thepresent invention, and for ink dots produced by a prior art inkjetprinting technology;

FIG. 5D provides bar graphs of deviation from convexity for ink dots oneach of the 19 fibrous substrates, according to some embodiments of thepresent invention, and for ink dots produced by a prior art inkjetprinting technology;

FIG. 5E-1 provides comparative bar graphs of the deviation fromroundness for ink dot constructions produced according to someembodiments of the present invention, vs. ink dots produced using areference ink formulation and printing method, for each of 10 fibroussubstrates;

FIG. 5E-2 provides comparative bar graphs of deviation from convexity ofthe ink dot constructions of FIG. 5E-1, for each of the 10 fibroussubstrates;

FIG. 5F-1 provides a magnified view of a field of ink dots on acommodity-coated fibrous substrate, produced using a commerciallyavailable aqueous, direct inkjet printer;

FIG. 5F-2 provides a magnified view of a field having an ink dotconstruction according to the present invention, in which thecommodity-coated substrate is identical to that of FIG. 5F-1;

FIG. 5G-1 provides a magnified view of a field of ink dots on anuncoated fibrous substrate, produced using a commercially availableaqueous, direct inkjet printer;

FIG. 5G-2 provides a magnified view of a field of an ink dotconstruction according to the present invention, in which the uncoatedsubstrate is identical to that of FIG. 5G-1;

FIGS. 5H-1-5H-3 provide magnified views of ink dot constructionsaccording to the present invention, in which an ink dot is printed oneach of various plastic substrates;

FIG. 5H-4 provides a magnified top view and a cross-sectional,instrumental view of an inventive ink film construction having an inkdot disposed on a plastic substrate;

FIGS. 5H-5-5H-7 each provide a magnified view of a field having an inkdot construction according to the present invention, each fieldcontaining ink dots printed onto a respective plastic substrate;

FIGS. 6A-1 to 6J-2 provide images of ink splotches or films obtainedusing various printing technologies on uncoated (6A-1 to 6E-1) andcoated (6F-1 to 6J-1) paper, and optical uniformity profiles (6A-2 to6J-2) therefor;

FIG. 7 is a ramped-down temperature sweep plot of dynamic viscosity as afunction of temperature, for several ink formulations of the presentinvention;

FIG. 8 is a ramped-down temperature sweep plot of dynamic viscosity as afunction of temperature, for several ink formulations of the presentinvention, vs. several commercially available inkjet inks;

FIG. 9 is a magnified view of the plot of FIG. 8, for lower viscosities;

FIG. 10 plots viscosity as a function of temperature for an ink residuerecovered from printed films, produced from ink formulations of thepresent invention;

FIG. 11 provides a plot of dynamic viscosity measurements at hightemperature for: a dry ink-residue of a black prior-art inkjetformulation; a dry ink-residue recovered from printed images of thatprior-art inkjet formulation; a dry ink-residue of a black inkformulation of the present invention; and a dry ink-residue recoveredfrom printed images of that inventive ink formulation;

FIG. 12 provides optical density measurements, along with a fitted curve(the lowermost curve) of the optical density achieved as a function offilm thickness, for a particular ink formulation;

FIG. 13 provides the optical density measurements of FIG. 12, plotted asa function of pigment content or calculated pigment thickness;

FIG. 14A provides a plot showing seven color gamut representationsaccording to ISO standard 15339; and

FIG. 14B plots a color gamut representation according to one embodimentof the present invention against color gamut representation #6 accordingto ISO standard 15339.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The ink film constructions according to the present invention may bebetter understood with reference to the drawings and the accompanyingdescription.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

Description of the Printing Process and System

The present invention is concerned with ink film constructions that maybe obtained in particular by the following printing process or using anyprinting system implementing such process. A printing process suitablefor the preparation of the ink films according to the invention includesdirecting droplets of an ink onto an intermediate transfer member toform an ink image, the ink including an organic polymeric resin and acolorant (e.g., a pigment or dye) in an aqueous carrier, and thetransfer member having a hydrophobic outer surface, each ink droplet inthe ink image spreading on impinging upon the intermediate transfermember to form an ink film (e.g., a thin film preserving a major part ofthe flattening and horizontal extension of the droplet present on impactor covering an area dependent upon the mass of ink in the droplet). Theink is dried while the ink image is being transported by theintermediate transfer member by evaporating the aqueous carrier from theink image to leave a residue film of resin and colorant. The residuefilm is then transferred to a substrate (e.g., by pressing theintermediate transfer member against the substrate to impress theresidue film thereupon). The chemical compositions of the ink and of thesurface of the intermediate transfer member are selected such thatattractive intermolecular forces between molecules in the outer skin ofeach droplet and on the surface of the intermediate transfer membercounteract the tendency of the ink film produced by each droplet to beadunder the action of the surface tension of the aqueous carrier, withoutcausing each droplet to spread by wetting the surface of theintermediate transfer member.

The printing process sets out to preserve, or freeze, the thin pancakeshape of each aqueous ink droplet, that is caused by the flattening ofthe ink droplet on impacting the surface of the intermediate transfermember (also termed the release layer), despite the hydrophobicity ofsuch layer. To achieve this objective, this novel process relies onelectrostatic interactions between molecules in the ink and in the outersurface of the transfer member, the molecules being either charged intheir respective medium or being mutually chargeable, becomingoppositely charged upon interaction between the ink and the releaselayer. Further details on the printing processes, and related systems,suitable for the preparation of ink constructions according to thepresent invention are disclosed in co-pending PCT Application Nos.PCT/IB2013/051716 (Agent's reference LIP 5/001 PCT); PCT/IB2013/051717(Agent's reference LIP 5/003 PCT); and PCT/IB2013/051718 (Agent'sreference LIP 5/006 PCT).

For illustration, a conventional hydrophobic surface, such as a siliconecoated surface, will yield electrons readily and is regarded asnegatively charged. Polymeric resins in an aqueous carrier are likewisegenerally negatively charged. Therefore, in the absence of additionalsteps being taken the net intermolecular forces will cause theintermediate transfer member to repel the ink and the droplets will tendto bead into spherical globules.

In the novel printing process suitable for the preparation of ink filmconstructions according to the invention, the chemical composition ofthe surface of the intermediate transfer member is modified to provide apositive charge. This may be achieved, for example, by including in thesurface of the intermediate transfer member (e.g., embedded in therelease layer) molecules having one or more Brønsted base functionalgroups and in particular nitrogen comprising molecules. Suitablepositively charged or chargeable groups include primary amines,secondary amines, and tertiary amines. Such groups can be covalentlybound to polymeric backbones and, for example, the outer surface of theintermediate transfer member may include amino silicones. Furtherdetails on intermediate transfer members including in their releaselayer Brønsted base functional groups, suitable for the preparation ofink film constructions according to the present invention are disclosedin co-pending PCT Application No. PCT/IB2013/051751 (Agent's referenceLIP 10/005 PCT).

Such positively chargeable functional groups of the molecules of therelease layer may interact with Brønsted acid functional groups ofmolecules of the ink. Suitable negatively charged or chargeable groupsinclude carboxylated acids such as having carboxylic acid groups(—COOH), acrylic acid groups (—CH₂═CH—COOH), methacrylic acid groups(—CH₂═C(CH₃)—COOH) and sulfonates such as having sulfonic acid groups(—SO₃H). Such groups can be covalently bound to polymeric backbones andpreferably be water soluble or dispersible. Suitable ink molecules mayfor example comprise acrylic-based resins such as an acrylic polymer andan acrylic-styrene copolymer having carboxylic acid functional groups.Further details on ink compositions that may be used to achieve the inkfilm constructions according to the present invention are disclosed inco-pending PCT Application No. PCT/IB2013/051755 (Agent's reference LIP11/001 PCT).

An alternative for negating the repelling of the ink droplets by thenegatively charged hydrophobic surface of the intermediate transfermember is to apply a conditioning or pre-treatment solution to thesurface of the intermediate transfer member to reverse its polarity topositive. One can look upon such treatment of the transfer member asapplying a very thin layer of a positive charge that is itself adsorbedonto the surface of the release layer but presents on its opposite sidea net positive charge with which the negatively charged molecules in theink may interact. Intermediate transfer members amenable to suchtreatment may, for example, comprise in their release layer silanol-,sylyl- or silane-modified or terminated polydialkyl-siloxane siliconesand further details on suitable ITMs are disclosed in co-pending PCTApplication No. PCT/IB2013/051743 (Agent's reference LIP 10/002 PCT).

Chemical agents suitable for the preparation of such conditioningsolutions, if required, have relatively high charge density and can bepolymers containing amine nitrogen atoms in a plurality of functionalgroups, which need not be the same and can be combined (e.g., primary,secondary, tertiary amines or quaternary ammonium salts). Thoughmacromolecules having a molecular weight from a few hundred to a fewthousand can be suitable conditioning agents, it is believed thatpolymers having a high molecular weight of 10,000 g/mole or more arepreferable. Suitable conditioning agents include guarhydroxylpropyltrimonium chloride, hydroxypropyl guarhydroxypropyl-trimonium chloride, linear or branched polyethylene imine,modified polyethylene imine, vinyl pyrrolidone dimethylaminopropylmethacrylamide copolymer, vinyl caprolactam dimethylaminopropylmethacrylamide hydroxyethyl methacrylate, quaternized vinyl pyrrolidonedimethylaminoethyl methacrylate copolymer, poly(diallyldimethyl-ammoniumchloride), poly(4-vinylpyridine) and polyallylamine. Further details onelective conditioning solutions suitable for the preparation of ink filmconstructions according to the present invention are disclosed inco-pending PCT Application No. PCT/IB2013/000757 (Agent's reference LIP12/001 PCT).

The disclosure of the afore-mentioned applications of the sameApplicant, incorporated by reference in their entirety as if fully setforth herein, may overlap with current disclosure, but it should be madeclear that the present invention is not restricted to such a process,using the intermediate transfer members, elective conditioningsolutions, and ink compositions exemplified therein. Relevant parts ofthe disclosure of these applications are included herein for theconvenience of the reader.

Description of the Ink

The inventors have found that that the inventive ink film constructions,if for instance obtained by the above-described printing system andprocess, may require an ink or an inkjet ink having particular chemicaland physical properties. These physical properties may include one ormore thermo-rheological properties.

According to one embodiment of the invention, there is provided anexemplary inkjet ink formulation (Example 1) containing:

Pigment: Jet Magenta DMQ (BASF)  2% Joncryl HPD 296 (35.5% watersolution) (BASF) 30% Glycerol (Aldrich) 20% BYK 345 (BYK) polyethermodified 0.5%  polydimethylsiloxane Water (distilled) Balance to 100%

Nominally, the resin solution may be, or include, an acrylic styreneco-polymer (or co(ethylacrylate metacrylic acid) solution. The averagemolecular weight may be less than 20,000 g/mole.

Preparation Procedure:

A pigment concentrate, containing pigment (10%), distilled water (70%)and resin, in the present case, Joncryl HPD 296 (20%), was made from theabove-described components. The pigment, water and resin were mixed andmilled using a homemade milling machine. Alternatively, the milling maybe performed using any one of many commercially available millingmachines deemed suitable by one of ordinary skill in the art. Theprogress of milling was controlled by particle size measurement(Malvern, Nanosizer). The milling was stopped when the average particlesize (d₅₀) reached about 70 nanometers (nm). The rest of the componentswere then added to the pigment concentrate to produce theabove-described exemplary inkjet ink formulation. After mixing, the inkwas filtered through a 0.5-micrometer (μm) filter.

The viscosity of the solution was about 9 cP at 25° C. Surface tensionat 25° C. was approximately 25 mN/m.

Various other milling procedures and milling apparatus will be apparentto those of ordinary skill in the art. Various commercially availablenano-pigments may be used in the inventive ink formulations. Theseinclude pigment preparations such as Hostajet Magenta E5B-PT andHostajet Black O-PT, both by Clariant as well as pigments demandingpost-dispersion processes, such as Cromophtal Jet Magenta DMQ andIrgalite Blue GLO, both by BASF.

One of ordinary skill in the art may readily recognize that variousknown colorants and colorant formulations may be used in the inventiveink or inkjet ink formulations. In one embodiment, such pigments andpigment formulations may include, or consist essentially of, inkjetcolorants and inkjet colorant formulations.

Alternatively or additionally, the colorant may be a dye. Examples ofdyes suitable for use in the ink formulations of the present inventioninclude: Duasyn Yellow 3GF-SF liquid, Duasyn Acid Yellow XX-SF, DuasynRed 3B-SF liquid, Duasynjet Cyan FRL-SF liquid (all manufactured byClariant); Basovit Yellow 133, Fastusol Yellow 30 L, Basacid Red 495,Basacid Red 510 Liquid, Basacid Blue 762 Liquid, Basacid Black X34Liquid, Basacid Black X38 Liquid, Basacid Black X40 Liquid (allmanufactured by BASF).

The following examples illustrate some ink compositions in accordancewith embodiments of the invention. Printing tests employing such inkcompositions in the method described in co-pending PCT application No.PCT/IB2013/051716 (Agent's reference LIP 5/001 PCT) show good transferto various paper and plastic substrates.

Example 2

An inkjet ink formulation was prepared containing:

Ingredient Function wt. % PV Fast Blue BG (Clariant) Pigment 2.3 NeocrylBT-9 (40% water Resin 16.5 dispersion) (DSM resins) Glycerol (Aldrich)Water-miscible 3.3 co-solvent Capstone FS-65 (DuPont) Non-ionic 0.1fluorosurfactant Water (distilled) — Balance to 100% Joncryl HPD 296(35.5% Dispersant 3.2 (solid resin) water solution) (BASF)Diethyleneglycol (Aldrich) Water-miscible 20 co-solvent Diethyl amine(Aldrich) pH adjustment 1 (basic)Preparation Procedure:

A pigment concentrate, containing pigment (14%), water (79%) and JoncrylHPD 296 (7%) were mixed and milled. The progress of milling wascontrolled on the basis of particle size measurements (Malvern,Nanosizer). The milling was stopped when the average particle size (d₅₀)reached 70 nm. The remaining materials were then added to the pigmentconcentrate and mixed. After mixing, the ink was filtered through a 0.5μm filter.

At 25° C., the viscosity of the ink thus obtained was about 13 cP, thesurface tension about 27 mN/m, and the pH 9-10.

Example 3

An inkjet ink formulation was prepared containing:

Ingredient Function wt. % Jet Magenta DMQ (BASF) Pigment 2.3 NeocrylBT-26 (40% water Resin 17.5 dispersion) (DSM resins) Monoethanol aminepH adjustment 1.5 (basic) Propylene glycol Water-miscible 20 co-solventN-methylpyrrolidone Water-miscible 10 co-solvent BYK 349 (BYK)surfactant 0.5 (silicone) Water (distilled) — Balance to 100%Preparation Procedure:

The pigment (10%), water (69%), Neocryl BT-26 (20%) and monoethanolamine (1%) were mixed and milled until the average particle size (d₅₀)reached 70 nm as described in Example 2. The rest of the materials werethen added to the pigment concentrate and mixed. After mixing, the inkwas filtered through a 0.5 μm filter.

At 25° C., the viscosity of the ink thus obtained was about 8 cP, thesurface tension was approximately 24 mN/m, and the pH was 9-10.

Example 4

An inkjet ink formulation was prepared containing:

Ingredient Function wt. % Jet Magenta DMQ (BASF) Pigment 2.2 Joncryl 683neutralized Dispersant 0.6 (solid resin) with KOH (BASF) Neocryl BT-9(40% water Resin 25 dispersion) (DSM resins) Ethylene glycolWater-miscible 25 co-solvent Propylene glycol Water-miscible 10co-solvent PEG 400 Water-miscible 2 co-solvent Glycerol Water-miscible 3co-solvent BYK 349 (BYK) surfactant 0.5 (silicone) Water (distilled) —Balance to 100%Preparation Procedure:

The pigment (12.3%), Joncryl 683 (3.3%) fully neutralized with a 30%solution of KOH (7.9%) and water (balance) were mixed and milled untilthe average particle size (d₅₀) reached 70 nm as described in Example 2.The rest of the materials were then added to the pigment concentrate andmixed. After mixing, the ink was filtered through a 0.5 μm filter.

At 25° C., the viscosity of the ink thus obtained was about 7 cP, thesurface tension was approximately 24 mN/m, and the pH was 7-8.

Example 5

An inkjet ink formulation was prepared containing:

Ingredient Function wt. % Carbon Black Mogul L Pigment 2.2 (Cabot)Joncryl 671 neutralized Dispersant 0.6 (solid resin) with KOH (BASF)NeoRad R-440 (40% water Resin 30 emulsion) (DSM resins) Propylene glycolWater-miscible 40 co-solvent 2-Amino-2-Methyl-1- pH adjustment 1Propanol (basic) Glycerol Water-miscible 5 co-solvent BYK 349 (BYK)surfactant 0.5 (silicone) Water (distilled) — Balance to 100%Preparation Procedure:

The pigment (14.6%), Joncryl 671 (3.9%) fully neutralized with a 30%solution of KOH (9.4%) and water (balance) were mixed and milled asdescribed in Example 2, until the average particle size (d₅₀) reached 70nm. The rest of the materials were then added to the pigment concentrateand mixed. After mixing, the ink was filtered through a 0.5 μm filter.

At 25° C., the viscosity of the ink thus obtained was about 10 cP, thesurface tension was approximately 26 mN/m, and the pH was 9-10.

With respect to the foregoing examples, various other milling procedureswill be apparent to those of ordinary skill in the art.

Example 6

An inkjet ink formulation was prepared containing:

Ingredient wt. % Hostajet Black O-PT 2.4 (Clariant) Neocryl BT-26, 40%water 18.0 dispersion (DSM resin) Monoethanol amine 1.5 Propylene glycol20 N-methylpyrrolidone 10 BYK 349 (BYK) 0.5 Water Balance to 100%

The above-provided formulation contains approximately 9.6% ink solids,of which 25% (2.4% of the total formulation) is pigment, and about 75%(40%*18%=7.2% of the total formulation) is resin, by weight.

Example 7

An inkjet ink formulation was prepared containing:

Duasyn Red 3B-SF liquid (Clariant)  4% Joncryl 296 HPD (35.5% solutionin water) 20% Diethylene glycol 20% N-methylpyrrolidone 10% BYK 3330.5%  Water (distilled) balance to 100%

Example 8

An inkjet ink formulation was prepared containing:

Ingredient Function wt. % Jet Magenta DMQ Pigment 2 Neocryl BT-102 (40%Resin 20 water dispersion) (8 = solid resin) (DSM resins) PropyleneGlycol Water-miscible 20 (Aldrich) co-solvent BYK 348 Non-ionic 0.2fluorosurfactant Disperbyk 198 Dispersant 2 Water (distilled) — Balanceto 100%Preparation Procedure:

A pigment concentrate, containing pigment (14%), water (72%) andDisperbyk 198 (14%) were mixed and milled. The progress of milling wascontrolled on the basis of particle size measurements (Malvern,Nanosizer). The milling was stopped when the average particle size (d₅₀)reached 70 nm. The remaining materials were then added to the pigmentconcentrate and mixed. After mixing, the ink was filtered through a 0.5μm filter.

At 25° C., the viscosity of the ink thus obtained was about 5.5 cP, thesurface tension about 25 mN/m, and the pH 6.5.

Example 9

An inkjet ink formulation was prepared containing:

Ingredient Function wt. % Novoperm Yellow P-HG Pigment 1.1 (Clariant)Paliotol Yellow L 1155 Pigment 1.1 (BASF) Joncryl 671 neutralizedDispersant 0.6 with KOH (BASF) (solid resin) NeoRad R-440 (40% waterResin 30 emulsion) (DSM resins) Propylene glycol Water-miscible 40co-solvent 2-Amino-2-Methyl-1- pH adjustment 1 Propanol (basic) BYK 349(BYK) surfactant 0.5 (silicone) Water (distilled) — Balance to 100%Preparation Procedure:

The pigment (14.6%), Joncryl 671 (3.9%), fully neutralized with a 30%solution of KOH (9.4%), and water (balance) were mixed and milled asdescribed in Example 2, until the average particle size (d₅₀) reached 70nm. The rest of the materials were then added to the pigment concentrateand mixed. After mixing, the ink was filtered through a 0.5 μm filter.

At 25° C., the viscosity of the ink thus obtained was about 9 cP, thesurface tension was approximately 26 mN/m, and the pH was 9-10.

Ink Film Constructions

Referring now to the drawings, FIG. 1A is a magnified image of aplurality of inkjet ink drops disposed near a top surface of a fibrous(paper) substrate, according to a prior-art technology. In this priorart ink and substrate construction, the inkjet ink drops have penetratedthe surface of the paper. Such a construction may be typical of varioustypes of paper, including uncoated paper, in which the paper may drawink carrier solvent and pigment within the matrix of the paper fibers.

FIG. 1B is a magnified image of a plurality of exemplary ink filmconstructions, such as inkjet ink film constructions, according to oneembodiment of the present invention. In contrast to the prior art inkand substrate construction provided in FIG. 1A, the inventive inkjet inkfilm construction may be characterized by well-defined individual inkfilms, disposed generally above, and adhering to, the fibrous substrate.The single-drop inkjet films shown in FIG. 1B exhibit superior opticaldensity. These characteristics are particularly notable when comparedwith the characteristics of the prior art ink and substrateconstruction, which exhibits poorly formed inkjet ink drops or splotcheshaving a low optical density.

A laser-microscope was used to produce comparative, highly magnifiedimages of prior-art ink splotches disposed under a top surface of asheet of paper. FIGS. 2A, 2B, and 2C are respective three-dimensionalmagnified images of a lithographic offset ink splotch (FIG. 2A), aliquid electro-photography (LEP) of HP-Indigo ink splotch (FIG. 2B), andan inkjet single-drop ink film (FIG. 2C) produced according to anembodiment of the present invention.

The inkjet single-drop ink film (or individual ink dot) was producedusing the inventive system and apparatus described herein, using theinventive ink formulation provided herein.

The above-referenced ink splotches of the prior art are commerciallyavailable. The offset sample was produced by a Ryobi 755 press, usingBestACK process ink by Roller Tiger (Toka Shikiso Chemical Industry).The LEP sample was produced by a HP Indigo 7500 digital press, using HPIndigo ink. With reference to the substrates, the uncoated substrateswere Mondy 170 gsm paper; the coated substrates were APP 170 gsm paper.

Laser microscopy imaging was performed using an Olympus LEXT 3Dmeasuring laser microscope, model OLS4000. The film (dot, drop, orsplotch) height above each substrate and the surface roughness of eachfilm or splotch analyzed were calculated by the microscope system in asemi-automatic fashion.

The perimeter of the offset ink splotch and the perimeter of the LEP inksplotch have a plurality of protrusions or rivulets, and a plurality ofinlets or recesses. These ink forms may be irregular, and/ordiscontinuous. By contrast, the inkjet ink dot (FIG. 2C) producedaccording to the present invention has a manifestly rounded, convex,shape. The perimeter of the ink film is relatively smooth, regular,continuous and well defined.

More particularly, projections of the ink film of the invention againstthe substrate surface (i.e., projections from a top view) tend to berounded, convex projections that form a convex set, i.e., for every pairof points within the projection, every point on the straight linesegment that joins them is also within the projection. Such a convex setis shown in FIG. 2D. By sharp contrast, the rivulets and inlets in theprojections of various prior-art define those projections as anon-convex sets, i.e., for at least one straight line segment within aparticular projection, a portion of that straight line segment isdisposed outside the projection, as illustrated in FIG. 2E.

It must be emphasized that ink images may contain an extremely largeplurality of individual or single ink films. For example, a 5 mm by 5 mmink image, at 600 dpi, may contain more than 10,000 of such single inkfilms. Therefore, it may be appropriate to statistically define the inkfilm constructions of the present invention: at least 10%, at least 20%,or at least 30%, and more typically, at least 50%, at least 70%, or atleast 90%, of the single ink dots, or projections thereof, may be convexsets. These ink dots are preferably selected at random.

It must be further emphasized that ink images may not have crispboundaries, particularly when those boundaries are viewed at highmagnification. Therefore, it may be appropriate to relax the definitionof the convex set whereby non-convexities (rivulets or inlets) having aradial length L_(r) (as shown in FIG. 2F) of up to 3,000 nm, up to 1,500nm, up to 1,000 nm, up to 700 nm, up to 500 nm, up to 300 nm, or up to200 nm, are ignored, excluded, or are “smoothed”, whereby the ink filmor ink film projection is considered to be a convex set. The radiallength L_(r) is measured by drawing a radial line L from the centerpoint C of the ink film image, through a particular rivulet or inlet.The radial length L_(r) is the distance between the actual edge of therivulet or inlet, and a smoothed projection P_(s) of the ink image,devoid of that rivulet or inlet, and matching the contour of the inkfilm image.

In relative terms, it may be appropriate to relax the definition of theconvex set whereby non-convexities (rivulets or inlets) having a radiallength of up to 15% of the film/drop/splotch diameter or averagediameter, up to 10%, and more typically, up to 5%, up to 3%, up to 2%,or up to 1%, are ignored, excluded, or are “smoothed”, as above, wherebythe ink film or ink film projection is considered to be a convex set.

FIGS. 3A, 3B, and 3C show surface roughness and surface heightmeasurements for the offset ink splotch, the LEP ink splotch, and theinkjet ink film provided in FIGS. 2A-2C. The instrumentally measuredheights (H) or thicknesses of the three samples were 762 nm for theoffset ink drop and 1104 nm for the LEP ink drop. By sharp contrast, theinstrumentally measured height of the inventive inkjet ink film(H_(film)) is 355 nm.

Repeating the above-described comparative study several times, usingadditional ink film specimens, appears to confirm these results for theprior art ink films. The LEP specimens typically had a height orthickness within a range of 900-1150 nm, while the lithographic offsetspecimens typically had a height or thickness within a range of 750-1200nm.

With regard to ink dots or films produced from jetted ink drops, we havefound that the maximum average supra-substrate thickness of the ink dotmay be calculated from the following equation:T _(AVG(MAX)) =V _(DROP) /[A _(FILM) *R _(VOL)]  (I)wherein:

-   T_(AVG(MAX)) is the maximum average supra-substrate thickness;-   V_(DROP) is the volume of the jetted drop, or a nominal or    characteristic volume of a jetted drop (e.g., a nominal volume    provided by the inkjet head manufacturer or supplier);-   A_(FILM) is the measured or calculated area of the ink dot; and-   R_(VOL) is a dimensionless ratio of the volume of the original ink    to the volume of the dried ink residue produced from that ink.

By way of example, an ink dot disposed on a plastic printing substratehas an area of 1075 square micrometers. The nominal size of the jetteddrop is 10.0±0.3 picoliters. R_(VOL) was determined experimentally: avessel containing 20.0 ml of the ink was heated at 130° C. until a dryresidue was obtained. The residue had a volume of 1.8 ml. Plugging intoEquation (I), T_(AVG(MAX))=10 picoliters/[1075 μm²*(20.0/1.8)]=837nanometers.

For generally round ink dots, the area of the ink dot may be calculatedfrom the ink dot diameter. Moreover, we have found that thedimensionless ratio R_(VOL) is generally about 10 for a wide variety ofinkjet inks.

While for inks that penetrate into the substrate, the actual averagethickness may be somewhat less than T_(AVG(MAX)), this calculation mayreliably serve as an upper bound for the average thickness. Moreover, inthe case of various plastic substrates, and in the case of variouspremium coated substrates, the maximum average supra-substrate thicknessmay substantially equal the average supra-substrate thickness. In thecase of various commodity-coated substrates, the maximum averagesupra-substrate thickness may approach the average supra-substratethickness, often within 100 nanometers, 200 nanometers, or 300nanometers.

With regard to ink dots or films produced from jetted ink drops, we havefound that the maximum average supra-substrate thickness of the ink dotmay be calculated from the following equation:T _(AVG(MAX)) =[V _(DROP)*ρ_(INK) *F _(nRESIDUE) ]/[A_(FILM)*ρ_(FILM)]  (II)wherein:

-   ρ_(INK) is the specific gravity of the ink;-   F_(nRESIDUE) is the weight of the dried ink residue divided by the    weight of the original ink; and-   ρ_(FILM) is the specific gravity of the ink.

Typically, the ratio of ρ_(INK) to ρ_(FILM) is approximately 1, suchthat Equation (II) may be simplified to:T _(AVG(MAX)) =[V _(DROP) *F _(nRESIDUE) ]/A _(FILM)  (III)

For a wide variety of aqueous ink jet inks, F_(nRESIDUE) roughly equalsthe weight fraction of solids in the ink jet ink.

Using the above-described Olympus LEXT 3D measuring laser microscope,the height of above the substrate surface was measured for various inkdot constructions.

Atomic Force Microscopy (AFM) is another, highly accurate measurementtechnique for measuring height and determining ink dot thickness on asubstrate. AFM measurements may be performed using commerciallyavailable apparatus, such as a Park Scientific Instruments ModelAutoprobe CP, Scanning Probe Microscopy equipped with Proscan version1.3 software (or later). The use of AFM is described in depth in theliterature, for example, by Renmei Xu, et al., “The Effect of Ink JetPapers Roughness on Print Gloss and Ink Film Thickness” [Department ofPaper Engineering, Chemical Engineering, and Imaging Center for Ink andPrintability, Western Michigan University (Kalamazoo, Mich.)].

With regard to the ink film constructions of the present invention, theinventors have found that the thickness of the dry ink film on thesubstrate may be adjusted by modifying the inkjet ink formulation. Toobtain a lower dot thickness, such modifying may entail at least one ofthe following:

-   -   reducing the resin to pigment ratio;    -   selecting a resin or resins enabling adequate film transfer,        even with a reduced resin to pigment ratio;    -   utilizing finer pigment particles;    -   reducing the absolute quantity of pigment.

To obtain thicker dots, at least one of the opposite modifications(e.g., increasing the resin to pigment ratio) may be made.

Such changes in the formulation may necessitate, or make advantageous,various modifications in the process operating conditions. The inventorshave found that lower resin to pigment ratios may require a relativelyhigh transfer temperature.

For a given inkjet ink formulation, an elevated transfer temperature mayreduce ink film thickness. Increased pressure of the pressure roller orcylinder toward the impression cylinder during the transfer of theresidue film to a substrate at the impression station may also reduceink film thickness. Also, ink film thickness may be reduced byincreasing the time of contact between the substrate and theintermediate transfer member, interchangeably termed herein an “imagetransfer member” and both abbreviated ITM.

All this notwithstanding, a practical minimum characteristic (i.e.,median) thickness or average thickness for ink films produced accordingto the present invention may be about 100 nm. More typically, such inkfilms may have a thickness of at least 125 nm, at least 150 nm, at least175 nm, at least 200 nm, at least 250 nm, at least 300 nm, at least 350nm, at least 400 nm, at least 450 nm, or at least 500 nm.

Using the above-provided film thickness guidelines, the inventors areable to obtain inventive film constructions having a characteristicthickness or average thickness of at least 600 nm, at least 700 nm, atleast 800 nm, at least 1,000 nm, at least 1,200 nm, or at least 1,500nm. The characteristic thickness or average thickness of a single dropfilm (or an individual ink dot) may be at most about 2,000 nm, at most1,800 nm, at most 1,500 nm, at most 1,200 nm, at most 1,000 nm, or atmost 900 nm. More typically, the characteristic thickness or averagethickness of a single drop film may be at most 800 nm, at most 700 nm,at most 650 nm, at most 600 nm, at most 500 nm, at most 450 nm, at most400 nm, or at most 350 nm.

Using the film thickness guidelines delineated hereinabove, theinventors are able to obtain inventive film constructions in which acharacteristic thickness or average thickness of the ink film may bewithin a range of 100 nm, 125 nm or 150 nm up to 1,800 nm, 1,500 nm,1,200 nm, 1,000 nm, 800 nm, 700 nm, 600 nm, 550 nm, 500 nm, 450 nm, 400nm, or 350 nm. More typically, the characteristic thickness or averagethickness of the ink film may be within a range of 175 nm, 200 nm, 225nm or 250 nm up to 800 nm, 700 nm, 650 nm, 600 nm, 550 nm, 500 nm, 450nm, or 400 nm. Suitable optical density and optical uniformity may beobtained, using the system, process, and ink formulations of the presentinvention.

Aspect Ratio

The inventors have found that the diameter of an individual ink dot inthe ink film constructions of the present invention may be adjusted,inter alia, by selection of a suitable ink delivery system for applyingthe ink (e.g., jetting) onto the ITM, and by adjusting the inkformulation properties (e.g., surface tension) to the requirements ofthe particular ink head.

This ink film diameter, D_(dot), or the average dot diameter on thesubstrate surface, D_(dotaverage), may be at least 10 micrometers, atleast 15 μm, or at least 20 μm, and more typically, at least 30 μm, atleast 40 μm, at least 50 μm, at least 60 μm, or at least 75 μm. D_(dot)or D_(dotaverage) may be at most 300 micrometers, at most 250 μm, or atmost 200 μm, and more typically, at most 175 μm, at most 150 μm, at most120 μm, or at most 100 μm.

Generally D_(dot) or D_(dotaverage) may be in the range of 10-300micrometers, 10-250 μm, 15-250 μm, 15-200 μm, 15-150 μm, 15-120 μm, or15-100 μm. More typically, with the currently used ink formulations, anda particular ink head, D_(dot) or D_(dotaverage) may be in the range of20-120 μm, 25-120 μm, 30-120 μm, 30-100 μm, 40-120 μm, 40-100 μm, or40-80 μm.

Each single-drop ink film or individual ink dot is characterized by adimensionless aspect ratio defined by:R _(aspect) =D _(dot) /H _(dot)wherein R_(aspect) is the aspect ratio; D_(dot) is a diameter,characteristic diameter, average diameter, or longest diameter of thedot; and H_(dot) is a thickness, characteristic thickness, or averagethickness of the dot, or the height of the top surface of dot withrespect to the substrate.

The aspect ratio may be at least 15, at least 20, at least 25, or atleast 30, and more typically, at least 40, at least 50, at least 60, atleast 75. In many cases, the aspect ratio may be at least at least 95,at least 110, or at least 120. The aspect ratio is typically below 200or below 175.

Penetration

In the ink film constructions of the present invention, the ink dot mayessentially be laminated onto a top surface of the printing substrate.As described herein, the form of the dot may be determined or largelydetermined prior to the transfer operation, and the dot is transferredas an integral unit to the substrate. This integral unit may besubstantially devoid of solvent, such that there may be no penetrationof any kind of material from the blanket transfer member into, orbetween, substrate fibers. The continuous dot, which may largely containorganic polymeric resin and colorant, adheres to, or forms a laminatedlayer on, the top surface of the fibrous printing substrate.

Such continuous dots are typically produced by various inkjettingtechnologies, such as drop-on-demand and continuous jettingtechnologies.

The organic polymeric resins used in conjunction with the presentinvention are typically water soluble or water dispersible.

FIGS. 3D and 3E provide schematic cross-sectional views of an inventiveink film construction 300 and an inkjet ink splotch or film construction370 of the prior art, respectively. Referring now to FIG. 3E, inkjet inkfilm construction 370 includes a single-drop ink splotch 305 adheringto, or laminated to, a plurality of substrate fibers 320 in a particularcontinuous area of a fibrous printing substrate 350. Fibrous printingsubstrate 350 may be, by way of example, an uncoated paper such as bond,copy, or offset paper. Fibrous printing substrate 350 may also be one ofvarious commodity coated fibrous printing substrates, such as a coatedoffset paper.

A portion of ink splotch 305 is disposed below the top surface ofsubstrate 350, between fibers 320. Various components of the ink,including a portion of the colorant, may penetrate the top surface alongwith the ink carrier solvent, to at least partially fill a volume 380disposed between fibers 320. As shown, a portion of the colorant maydiffuse or migrate underneath fibers 320, to a volume 390 disposedbeneath fibers 320. In some cases (not shown), some of the colorant maypermeate into the fibers.

By sharp contrast, inventive ink film construction 300 (in FIG. 3D)includes an integral continuous ink dot such as individual ink dot 310,disposed on, and fixedly adhering (or laminated) to, a top surface of aplurality of substrate fibers 320, in a particular continuous area offibrous printing substrate 350. The adhesion or lamination may be,primarily or substantially, a physical bond. The adhesion or laminationmay have little, or substantially no, chemical bonding character or morespecifically, no ionic bonding character.

Ink dot 310 contains at least one colorant dispersed in an organicpolymeric resin. Within the particular continuous area of fibroussubstrate 350, there exists at least one direction (as shown by arrows360—several directions) perpendicular to the top surface of printingsubstrate 350. With respect to all the directions normal to this topsurface over all of the dot area, ink dot 310 is disposed entirely abovethe area. The volume 380 between fibers 320 and the volume 390underneath fibers 320 are devoid, or substantially devoid, of colorant,resin, and any and all components of the ink.

The thickness (H_(dot)) of single-drop ink film or individual ink dot310 may be at most 1,800 nm, at most 1,500 nm, at most 1,200 nm, at most1,000 nm, or at most 800 nm, and more typically, at most 650 nm, at most600 nm, at most 550 nm, at most 500 nm, at most 450 nm, or at most 400nm. The thickness (H_(dot)) of single-drop ink dot 310 may be at least50 nm, at least 100 nm, or at least 125 nm, and more typically, at least150 nm, at least 175 nm, at least 200 nm, or at least 250 nm. The extentof penetration of an ink into a printing substrate may be quantitativelydetermined using various analytical techniques, many of which will beknown to those of ordinary skill in the art. Various commercialanalytical laboratories may perform such quantitative determination ofthe extent of penetration.

These analytical techniques include the use of various stainingtechniques such as osmium tetroxide staining (see Patrick Echlin,“Handbook of Sample Preparation for Scanning Electron Microscopy andX-Ray Microanalysis” (Springer Science+Business Media, LLC 2009, pp.140-143).

One alternative to staining techniques may be particularly suitable toinks containing metals such as copper. Time of Flight Secondary Ion MassSpectrometry (TOF-SIMS) was performed using a TOF-SIMS V Spectrometer[Ion-ToF (Münster, Germany)]. This apparatus provides elemental andmolecular information with regard to the uppermost layer of organic andinorganic surfaces, and also provides depth profiling and imaging havingdepth resolution on the nanometric scale, submicron lateral resolutionand chemical sensitivity on the order of 1 ppm.

Translation of the raw data of the TOF-SIMS into concentration may beperformed by normalizing the signals obtained to the carbon (C+)concentration measured by X-ray Photoelectron Spectroscopy (XPS), in thesample. The XPS data was obtained using a Thermo VG Scientific SigmaProbe (England). Small area chemical analysis of solid surfaces withchemical bonding information was obtained by using a microfocused (from15 to 400 μm) monochromated x-ray source. Angle resolved information isobtained with and without tilting the sample. This enables depthprofiling with good depth resolution.

As a baseline, the atomic concentration of copper within a fibrous papersubstrate was measured, as a function of depth. The atomic concentrationof copper was found to be substantially zero at the surface, down to adepth of several micrometers. This procedure was repeated for twocyan-colored inkjet ink film constructions of the prior art, and for acyan-colored ink film construction of the present invention.

FIG. 3F provides a graph plotting the atomic concentration of copper[Cu] within the ink dot and within the fibrous paper substrate, as afunction of the approximate depth, within a first cyan-colored inkjetink film construction of the prior art. The initial [Cu], measured nearthe top surface of the cyan-containing ink film construction, wasapproximately 0.8 atomic %. Within a depth of about 100 nm, [Cu] droppedsteadily to about 0.1 atomic %. Over a depth range of about 100 nm-1,000nm, [Cu] dropped from about 0.1 atomic % to about zero. Thus, it isevident that the inkjet ink pigment has penetrated into the fibrouspaper substrate, possibly attaining a penetration depth of at least 700nm, at least 800 nm, or at least 900 nm.

FIG. 3G provides a graph plotting the atomic concentration of copperwithin the ink dot construction, as a function of the approximate depth,within a second cyan-colored inkjet ink film construction of the priorart. The initial atomic concentration of copper [Cu] within the ink dotconstruction, measured near the top surface, was approximately 0.02atomic %. This concentration was generally maintained over a depth ofabout 3,000 nm. Over a depth range of about 3,000 nm to almost 6,000 nm,[Cu] dropped very gradually to about 0.01 atomic %. It would appear thatthis prior-art construction has little or no ink film on the surface ofthe substrate, and that penetration of the pigment into the substratewas pronounced (at least 5-6 micrometers).

FIG. 3H provides graphs plotting the atomic concentration of copperwithin the ink dot and within the fibrous paper substrate, as a functionof the approximate depth, within a cyan-colored ink film construction ofthe present invention. The two graphs represent measurements made at twodifferent positions (“Sample 1” and “Sample 2”) on the inventive ink dotconstruction. The initial atomic concentration of copper [Cu], measurednear the top surface, was approximately 0.2 or 0.4 atomic % for Sample 1and Sample 2, respectively. Over a depth of about 75 to about 100 nm,[Cu] steadily increased to about 0.5 or 0.7 atomic % for the respectiveSamples. At a depth of about 100 nm to about 175 nm, [Cu] began to dropsharply, attaining a copper concentration of substantially zero at adepth of 200-250 nm, for both Samples. It would appear that theinventive construction is solely disposed on the surface of thesubstrate, and that pigment penetration into the substrate wasnegligible or substantially negligible, both in terms of penetrationdepth and in terms of the penetration quantity or fraction.

Without wishing to be bound by theory, the inventors believe that theinitial rise in [Cu] over the depth of 75-100 nm may be attributed tothe orientation of the ink dot due to micro-contours of the substrate,and to surface roughness of the ink dot itself. Similarly, the drop in[Cu] to substantially zero at a depth of 200-250 nm may be attributed tothe micro-contours of the substrate: for a given cross-section within,and generally parallel to the face or top surface of the substrate, someof the ink dot may be present (see dashed line in FIG. 3D). Thisnotwithstanding, the ink dot being is entirely disposed above thesubstrate, with respect to a direction perpendicular to the substratesurface.

Surface Roughness

Using laser microscopy imaging and other techniques, the inventors haveobserved that the top surface of the ink dots in the ink filmconstructions of the present invention may be characterized by a lowsurface roughness, particularly when the substrates of thoseconstructions have a high paper (or substrate) gloss.

Without wishing to be limited by theory, the inventors believe that therelative flatness or smoothness of the ink film constructions of thepresent invention may largely be attributed to the smoothness of therelease layer on the surface of the ITM, and to the inventive system andprocess in which the emerging ink film surface substantially complementsthat of that surface layer, and in which the developing ink film imagemay substantially retain or completely retain that complementarytopography through the transfer onto the printing substrate.

Referring now to FIG. 4A, FIG. 4A is an image of the surface of arelease layer of an ITM or blanket used in accordance with the presentinvention. While the surface may be nominally flat, various pockmarks(recesses) and protuberances, typically of the order of 1-5 μm, may beobserved. Many of these marks have sharp, irregular features. An imageof an ink dot surface produced using this blanket, provided in FIG. 4B,displays topographical features that are strikingly similar in nature tothose shown in FIG. 4A. The dot surface is peppered with a largeplurality of marks having sharp, irregular features, which stronglyresemble (and are within the same size range as) the irregular marks inthe blanket surface.

A smoother blanket was installed; FIG. 4C provides an image of therelease layer of this blanket. The irregular pockmarks of FIG. 4A areconspicuously absent. Dispersed on the highly smooth surface are highlycircular surface blemishes, perhaps made by air bubbles, typicallyhaving a diameter of about 1-2 μm. An image of an ink dot surfaceproduced using this blanket, provided in FIG. 4D, displays topographicalfeatures that are strikingly similar in nature to those shown in FIG.4C. This image has virtually no distinctive pockmarks, but has a numberof highly circular surface blemishes that are strikingly similar in sizeand form to those shown of the blanket surface.

Dot Perimeter Characterization

The perimeter of various ink dots or films of the prior art maycharacteristically have a plurality of protrusions or rivulets, and aplurality of inlets or recesses. These ink forms may be irregular,and/or discontinuous. By sharp contrast, the inkjet ink dot producedaccording to the present invention characteristically has a manifestlyrounded, convex, circular shape. The perimeter of the ink dot of theinvention may be relatively smooth, regular, continuous and welldefined. Ink dot roundness, convexity, and edge raggedness arestructural parameters used to evaluate or characterize shapes, oroptical representations thereof.

It can readily be observed, by comparing the magnified images of theprior-art ink forms of FIG. 1A with the inventive ink dots of FIG. 1B,or by comparing the magnified images of the prior-art ink forms of FIGS.2A and 2B with the inventive ink dots of FIG. 2C, that the appearance ofthe ink dots of the present invention is manifestly distinct from theseprior-art ink forms. That which is readily observed by the human eye maybe quantified using image-processing techniques. Variouscharacterizations of the ink forms are described hereinbelow, after adescription of the image acquisition method.

Acquisition Method

(1) For each of the known printing technologies to be compared in thestudy, single dots, splotches, or film images printed on coated paperand on uncoated paper were used. In the initial tests, the coated paperused was Condat Gloss® 135 gsm, or similar; the uncoated paper used wasMulti Fine Uncoated, 130 gsm, or similar. Subsequently, a wide varietyof substrates were used, including numerous coated and uncoated fibroussubstrates, and various plastic printing substrates.

(2) Regarding the inventive printing technology of the Applicant, singledrop dot images were printed on coated paper and on uncoated paper. Carewas taken to select substrates having similar characteristics to thesubstrates of the known ink-dot constructions used in (1).

(3) The acquisition of the dot images was performed using an OLS4000(Olympus) microscope. Those of ordinary skill in the art know how toadjust the microscope to achieve the requisite focus, brightness andcontrast, so that the image details will be highly visible. These imagedetails include the dot contour, the color variance within the dot area,and the fibrous structure of the substrate surface.

(4) The images were taken with an ×100 optical zoom lens having aresolution of 129 micrometers×129 micrometers. This high resolution maybe essential in obtaining fine details of the dot and of the fibrousstructure of the substrate surface.

(5) The images were saved in uncompressed format (Tiff) having aresolution of 1024×1024 pixels. Compression formats may lose image data.

(6) Generally, a single dot or splotch was evaluated for each printingtechnology. From a statistical point of view, however, it may beadvantageous to obtain 15 dot images (at least) for each type ofhard-copy print being analyzed, and to manually select the 10 (at least)most representative dot images for image processing. The selected dotimages should be representative in terms of dot shape, contour and colorvariation within the dot area. Another approach to print dot sampling,termed “field of view”, is described hereinbelow.

Dot Contour Computation

The dot images were loaded to the image-processing software(ImageXpert). Each image was loaded in each of the Red, Green and Bluechannels. The processing channel was selected based on a highestvisibility criterion. For example, for cyan dots, the Red channeltypically yielded the best dot feature visibility, and was thus selectedfor the image processing step; the Green channel was typically mostsuitable for a magenta dot. The dot edge contour was detected(automatically computed), based on a single threshold. Using a “fullscreen view” mode on a 21.5″ display, this threshold was chosen manuallyfor each image, such that the computed edge contour would best match thereal and visible dot edge. Since a single image-channel was processed,the threshold was a gray value (from 0 to 255, the gray value being anon color value).

A computed perimeter value was obtained from the image-processingsoftware (e.g., ImageXpert), the perimeter value being the sum of alldistances between the adjacent, connected pixels at the edge of the dotor splotch. If, for example, the XY coordinates for adjacent pixels are(x1, y1) and (x2, y2), the distance is √[(x2−x1)²+(y2−y1)²], while theperimeter equals Σ{√[(x_(i+1)−x_(i))²+(y_(i+1)−y_(i))²]}.

In various embodiments of the invention, it is desired to measure thelength of the perimeter of an ink dot. An alternative method formeasuring the perimeter length will now be described. As a first step,an image comprising an ink dot is used as input for an algorithm thatoutputs perimeter length. The pixel dimension M×N of the image may bestored in a two-element array or an ordered pair image_pixel_size. Anexample of the value of the image_pixel_size is 1280,760—in this exampleM=1280 and N=760. This corresponds to an image 1280 pixels in thehorizontal axis and 760 pixels in the vertical axis. Subsequently, theimage magnification ratio or scale is obtained and stored in variableimage_magnification. One example of variable image_magnification is 500.When comparing perimeters between ink dots in first and second images itis mandatory that the variables image_pixel_size and image_magnificationof the two images are equal. It is now possible to calculate thecorresponding length of one square pixel—i.e., the side length in areal-world length units (e.g., microns) or a pixel. This value is storedin a variable pixel_pitch. One example of the variable pixel_pitch is0.05 μm. The image is now converted to grayscale by methods known to theskilled artisan. One proposed method is converting the input image, theimage typically in an sRGB color space, to the L*a*b* color space. Oncethe image is in the Lab color space, the values for the variables a andb are changed to zero. It is now possible to apply an edge detectionoperator to the image. The preferred operator is a Canny edge detectionoperator. However, any operator known in the art may be applied. Theoperators are not limited to first order derivatives, such as the cannyoperator, but rather open to second derivatives as well. Furthermore, acombination of operators may be used in order to obtain results that maybe compared between operators and subsequently remove “unwanted” edges.It may be favorable to apply a smoothing operator such as a Gaussianblur prior to applying the edge detection operator. The threshold levelapplied when applying the edge detection operator is such that an edgethat forms an endless loop is first obtaining in the area between theformerly described minimal circumference Ink dot engulfing circle andthe maximal circumference ink dot enclosed circle. A thinning operatoris now implemented to render the endless loop edge substantially onepixel wide. Any pixel that is not a part of the endless loop edge hasits L* value change to zero, while any pixel that is part of the endlessloop edge has its L* value change to 100. The endless loop edge isdefined as the perimeter of the ink dot. A pixel link is defined as astraight line connecting to pixels. Each pixel along the perimeterincorporates two pixel links, a first pixel link and a second pixellink. These two pixel links define a pixel link path within a singlepixel. In this method of computing perimeter length, each pixel is asquare pixel. Therefore, each pixel link may form a line from the centerof the pixel to one of eight possible nodes. The possible nodes beingthe corners of the pixel or a midpoint between two neighboring cornersof the pixel. Nodes at the corners of the pixels are of the type node_1one nodes at the midpoint between two corners are of type node_2. Assuch, there are six possibilities of pixel link paths within a pixel.These can be categorized into three groups. Group A, B, and C. Eachgroup has its own corresponding coefficient, namely, coefficient_A,coefficient_B, and coefficient_C. The value of coefficient_A is 1, thevalue of coefficient_B is the sqrt(2), and the value of coefficient_C is(1+sqrt(2))/2. Group A contains pixels whose pixel link path coincideswith nodes of type node_2. Group B contains pixels whose pixel link pathcoincides with nodes of type node_1. Group C contains pixels whose pixellink path coincides with nodes of type node_1 and type node_2. It is nowpossible to calculate the pixel length of the perimeter. The pixellength of the perimeter is calculated by summing all of the pixels inthe perimeter multiplied by their corresponding coefficient. This valueis stored in variable perimeter_pixel_length. It is now possible tocalculate the actual length of the ink dot perimeter. This is done bymultiplying perimeter_pixel_length by pixel_pitch.

Roundness

A dimensionless roundness factor (ER), may be defined by:ER=P ²/(4π·A)wherein P is the measured or calculated perimeter, and A is the measuredor computed area within the ink film, dot or splotch. For a perfectlysmooth and circular ink dot, ER equals 1.

The deviation from a round, smooth shape may be represented by theexpression (ER−1). For a perfectly circular, idealized ink dot, thisexpression equals zero.

The R-square of the roundness factor may be computed for each of the 10most representative dot images selected for each type of printingtechnology, and averaged into a single value.

For ink film constructions in which the fibrous substrate (e.g., paper)is uncoated, or for ink film constructions in which the fibroussubstrate is coated with a coating such as the commodity coating incoated offset paper (or such as coatings which enable the carrier fromtraditional water-based inkjet ink to reach the paper fibers), thedeviation from a round, smooth round shape [(ER−1), henceforth,“deviation”] for the ink dots of the present invention is not ideal, andwill exceed 0.

Exemplary ink film images disposed on coated (FIG. 5A) and uncoated(FIG. 5B) substrates are provided for the following printers: HP DeskJet9000 (1); Digital press: HP Indigo 7500 (2); Lithographic Offset: Ryobi755 (3); and Xerox DC8000 (4), and for the inventive digital printingtechnology (5). These ink film images were obtained generally accordingto the image acquisition method detailed hereinabove. Next to eachoriginal image is provided a corresponding processed, black and whiteimage in which the image-processor computed contour of the ink dot,film, or splotch is highlighted, and in which the computed contours aremanifestly similar to the contours of the original images.

For all tested coated fibrous (paper) substrates, the typical,individual inventive ink dots exhibited a deviation from a round, smoothshape (ER−1) of 0.16 to 0.27. By sharp contrast, the deviation fromroundness of the coated prints of the various prior-art technologiesranged from 1.65 to 7.13.

For all tested uncoated fibrous (paper) substrates, the typical,individual inventive ink dots exhibited a deviation (ER−1) of 0.28 to0.89. On each of these substrates, some of the inventive ink dotsexhibited a deviation (ER−1) of at most 0.7, at most 0.6, at most 0.5,at most 0.4, at most 0.35, at most 0.3, at most 0.25, or at most 0.20.

By sharp contrast, the deviation from roundness of ink films in theuncoated prints of the various prior-art technologies ranged from 2.93to 14.87.

An additional study was performed on 19 fibrous substrates of varyingphysical and chemical properties. The substrates included coated anduncoated substrates, and wood-free and mechanical substrates. Thesubstrates are characterized by differences in thickness, density,roughness (e.g., Bendtsen number) or smoothness (gloss), etc. Thesesubstrates are identified and partially characterized in Table 1.

In the case of several substrates, the deviation from roundness of theinventive ink dot constructions is compared with ink images produced bya commercial inkjet printer (using compatible ink cartridges provided bythe manufacturer) in the bar graphs provided in FIG. 5C.

It must be emphasized that in this additional study, the ink-filmconstructions of the present invention were produced on an inventivepilot, semi-automatic digital printing press, in which the transfer ofthe ink dots from the ITM to the printing substrate is performedmanually, and consequently, with an impression pressure that may besomewhat lower, and more variable, than the previously describedcommercial prototype of a fully-automatic digital printing press of thepresent invention.

For example, substrate number 6, Condat Gloss 135, is the same substrateused above for the inventive ink dot shown in FIG. 5A. However, thedeviation from roundness achieved by a typical ink dot was 0.362, whichrepresents a larger deviation than the deviations (0.16 to 0.27) of allof the inventive ink dots printed by the commercial prototype of theinventive digital press printer. However, a portion (albeit lower) ofthe inventive ink dots produced on the pilot, semi-automatic digitalprinting press attained deviations as low or lower than the lowesttypical deviation (0.16) achieved on the commercial prototype digitalpress printer.

TABLE 1 Inventive Dots Deviation From Non- GSM Roundness Convexity #Substrate name (g/m²) Type (ER-1) (1-CX) 1 Chromo Matte 300 300 Coated0.361 0.006 2 Chromo Matte Garda 130 130 Coated Wood Free 0.656 0.009 3Chromo Matte Graphic 130 130 Coated 0.305 0.008 4 Chromo Matte Graphic170 170 Coated 0.395 0.011 5 Condat Gloss 90 90 Coated 0.218 0.005 6Condat Gloss 135 135 Coated 0.362 0.006 7 Condat Gloss 225 225 Coated0.229 0.004 8 Dalum Glossy recycled 250 Coated Recycled 0.357 0.008 9Gruppo Cordenons - Ivolaser 120 Uncoated 0.120 0.007 Digital 10 HolmenPlus 49 Uncoated 0.621 0.021 Mechanical 11 Holmen XLNT 55 Uncoated 0.5150.020 Mechanical 12 Invercote G 300 SBS board, C1S 0.393 0.008 13 LeipaUltraLUX Semi Gloss 90 Low Weight 0.449 0.009 Coated 14 Norske SkogNorCote Bruck H 70 LWC Coated 0.548 0.011 15 Sappi Magno Satin 170Coated Wood Free 0.174 0.007 16 Sappi Magno Star 250 Coated Wood Free0.406 0.006 17 Torras Matte 90 90 Coated 0.410 0.014 18 Torras Matte 130130 Coated 0.404 0.015 19 Torras Matte 170 170 Coated 0.078 0.004

Considering coated and uncoated fibrous (paper) substrates together, thedeviation from roundness of the inventive ink dots is greater than zero,and may be at least 0.01, at least 0.02, or at least 0.03. For each ofthe 19 tested fibrous substrates provided in Table 1, at least some ofthe inventive ink dots exhibited a deviation from roundness (on bothuncoated and coated fibrous substrates) of at most 0.30, at most 0.25,at most 0.20, at most 0.15, or at most 0.12.

The inventive ink dots, when adhering to coated (or commodity-coated)fibrous substrates, may typically exhibit a deviation of at most 0.20,at most 0.18, at most 0.16, at most 0.14, at most 0.12, or at most 0.10.For each of the coated substrates provided in Table 1, at least some ofthe inventive ink dots exhibited a deviation from roundness of at most0.25, at most 0.20, at most 0.15, at most 0.12, at most 0.10, at most0.09, at most 0.08, at most 0.07, or at most 0.06.

Because, as noted above, ink images may contain an extremely largeplurality of individual ink dots or single drop ink films, it may bemeaningful to statistically define the inventive ink film constructionswherein at least 20% or at least 30%, and in some cases, at least 50%,at least 70%, or at least 90%, of the inventive ink dots (or inventivesingle-drop ink dots), disposed on any uncoated or coated (orcommodity-coated) fibrous substrate, and randomly selected, may exhibita deviation from roundness that is at least 0.01 or at least 0.02, andmay be at most 0.8, at most 0.65, at most 0.5, at most 0.35, at most0.3, at most 0.25, at most 0.2, at most 0.15, at most 0.12, or at most0.10.

As with a single ink dot or an individual single-drop ink dot, at least20% or at least 30%, and more typically, at least 50%, at least 70%, orat least 90%, of the inventive ink dots (or the inventive single-dropink dots), disposed on any coated (or commodity-coated) fibroussubstrate, and randomly selected, may exhibit a deviation from roundnessthat is at least 0.01 or at least 0.02, and may be at most 0.8, at most0.65, at most 0.5, at most 0.35, or at most 0.3, and more typically, atmost 0.25, at most 0.2, at most 0.15, at most 0.12, at most 0.10, atmost 0.08, at most 0.07, or at most 0.06.

Additional characterizations pertaining to deviation from roundness areprovided hereinbelow.

Convexity

As described hereinabove, the ink dots or films of the prior art maycharacteristically have a plurality of protrusions or rivulets, and aplurality of inlets or recesses. These ink forms may be irregular,and/or discontinuous. By sharp contrast, the inkjet ink film producedaccording to the present invention characteristically has a manifestlyrounded, convex, circular shape. Dot convexity, or deviation therefrom,is a structural parameter that may be used to evaluate or characterizeshapes, or optical representations thereof.

The image acquisition method may be substantially identical to thatdescribed hereinabove.

Convexity Measurement

The dot images were loaded to the image-processing software(ImageXpert). Each image was loaded in each of the Red, Green and Bluechannels. The processing channel was selected based on a highestvisibility criterion. For example, for cyan dots, the Red channeltypically yielded the best dot feature visibility, and was thus selectedfor the image processing step; the Green channel was typically mostsuitable for a magenta dot. The dot edge contour was detected(automatically computed), based on a single threshold. Using a “fullscreen view” mode on a 21.5″ display, this threshold was chosen manuallyfor each image, such that the computed edge contour would best match thereal and visible dot edge. Since a single image-channel was processed,the threshold was a gray value (from 0 to 255, the gray value being anon color value).

A MATLAB script was created to compute the ratio between the area of theminimal convex shape that bounds the dot contour and the actual area ofthe dot. For each ink dot image, the (X,Y) set of points of the dot edgecontour, created by ImageXpert, was loaded to MATLAB.

In order to reduce the sensitivity of measurement to noise, the dot edgewas passed through a Savitzky-Golay filter (image-processing low-passfilter) to slightly smooth the edge contour, but without appreciablymodifying the raggedness characteristic thereof. A window frame size of5 pixels was found to be generally suitable.

Subsequently, a minimal-area convex shape was produced to bound thesmoothed edge contour. The convexity ratio between the convex shape area(CSA) and the actual (calculated) dot or film area (AA) was thencomputed as follows:CX=AA/CSAThe deviation from this convexity ratio, or “non-convexity”, isrepresented by 1−CX, or DC_(dot).

For the above-described exemplary ink dot images disposed on coated(FIG. 5A) and uncoated (FIG. 5B) substrates, the convex shape area (CSA)is shown surrounding the actual dot area (AA), and the convexity ratiois provided in percentage form.

In the ink film images of FIG. 5A, disposed on coated substrates, theconvexity of the print images of the various prior-art technologiesranged from 87.91% to 94.97% (˜0.879 to 0.950 in fractional form),corresponding to a deviation from convexity of 0.050 to 0.121. By sharpcontrast, the inventive ink dot exhibited a convexity of 99.48%(˜0.995), corresponding to a deviation from convexity of about 0.005.This deviation is about 1/10 to 1/25 of the deviation exhibited by thevarious prior-art technologies. In absolute terms, the deviation is atleast 0.04 less than the deviation exhibited by the various prior-arttechnologies.

The difference between the inventive dot images and those of the variousprior-art technologies may be more striking on uncoated substrates. Inthe ink film images of FIG. 5B, disposed on uncoated substrates, theconvexity of the print images of the various prior-art technologiesranged from 65.58% to 90.19% (˜0.656 to 0.902 in fractional form),corresponding to a deviation from convexity of 0.344 to 0.098. By sharpcontrast, the inventive ink dot exhibited a convexity of 98.45%(˜0.985), corresponding to a deviation from convexity of about 0.015.This deviation is at least ⅙ to 1/20 of the deviation exhibited by thevarious prior-art technologies. In absolute terms, the deviation is atleast 0.08 less than the deviation exhibited by the various prior-arttechnologies.

Another study, described hereinabove, was performed, in which theink-film constructions of the present invention were produced on 19different fibrous substrates. In Table 1, the non-convexity of typicalinventive dots is provided. The non-convexity of the ink dots in theink-film constructions is graphically presented in the bar graphsprovided in FIG. 5D.

As in the deviation from roundness study, the printed dots of thepresent invention exhibit superior convexity with respect to the priorart images, for any given substrate, coated or uncoated.

For all 19 tested fibrous substrates, typical inventive ink dotsexhibited a non-convexity of 0.004 to 0.021. For each of the 19 testedfibrous substrates, at least some of the inventive ink dots exhibited anon-convexity of at most 0.018, at most 0.016, at most 0.015, at most0.014, or at most 0.013.

For all tested commodity coated fibrous substrates, typical inventiveink dots exhibited a non-convexity of 0.004 to 0.015. For each of thesecoated fibrous substrates, at least some of the inventive ink dotsexhibited a non-convexity of at most 0.014, at most 0.012, at most0.010, at most 0.009, at most 0.008, or at most 0.007.

For each of the uncoated substrates, at least some of the inventive inkdots exhibited a non-convexity of at most 0.03, at most 0.025, at most0.022, at most 0.020, at most 0.018, at most 0.016, at most 0.015, atmost 0.014, or at most 0.013.

Because, as noted above, ink images may contain an extremely largeplurality of individual dots or single drop ink films (at least 20, atleast 100, or at least 1,000), it may be meaningful to statisticallydefine the inventive ink film constructions wherein at least 10%, atleast 20%, or at least 30%, and in some cases, at least 50%, at least70%, or at least 90%, of the inventive ink dots (or inventivesingle-drop ink dots), disposed on any uncoated or coated (orcommodity-coated) fibrous substrate, and randomly selected, may exhibita non-convexity of at most 0.04, at most 0.035, at most 0.03, at most0.025, at most 0.020, at most 0.017, at most 0.014, at most 0.012, atmost 0.010, at most 0.009, at most 0.008, or at most 0.007.

At least 10%, at least 20%, or at least 30%, and in some cases, at least50%, at least 70%, or at least 90%, of these inventive ink dots (orinventive single-drop ink dots) may exhibit a non-convexity of at least0.001, at least 0.002, or at least 0.0025.

As with a single ink dot or an individual single-drop ink dot, at least10%, at least 20%, or at least 30%, and more typically, at least 50%, atleast 70%, or at least 90%, of the inventive ink dots (or the inventivesingle-drop ink dots), disposed on any uncoated or coated (or“commodity-coated”) fibrous substrate, and randomly selected, mayexhibit a non-convexity within a range of 0.001-0.002 to 0.05,0.001-0.002 to 0.04, 0.001-0.002 to 0.035, 0.001-0.002 to 0.030,0.001-0.002 to 0.025, 0.001-0.002 to 0.020, 0.001-0.002 to 0.015,0.001-0.002 to 0.012, or 0.001 to 0.010.

For any coated or “commodity-coated” fibrous printing substrate, thesesame dots may exhibit a lower non-convexity, within a range of0.001-0.002 to 0.020, 0.001-0.002 to 0.015, 0.001-0.002 to 0.012,0.001-0.002 to 0.010, 0.001 to 0.008, 0.001 to 0.007, 0.001 to 0.006,0.001 to 0.005, or 0.001 to 0.004.

For any uncoated fibrous printing substrate, these same dots may exhibita non-convexity within a range of 0.001-0.002 to 0.05, 0.001-0.002 to0.04, 0.001-0.002 to 0.035, 0.001-0.002 to 0.030, 0.001-0.002 to 0.025,0.001-0.002 to 0.020, 0.001-0.002 to 0.015, 0.001-0.002 to 0.012, or0.001 to 0.010.

Additional characterizations pertaining to ink dot convexity areprovided hereinbelow.

Reference Ink

The ink dots in the ink dot constructions of the present invention mayexhibit consistently good shape properties (e.g., convexity, roundness,edge raggedness, and the like), irrespective, to a large degree, of theparticular, local topographical features of the substrate, andirrespective, to some degree, of the type of printing substrate (e.g.,commodity-coated or uncoated printing substrates). However, the shapeproperties of the ink dots in the ink dot constructions of the presentinvention are not completely independent of the type of printingsubstrate, as evidenced by the bottom frames of FIG. 5A (coated fibroussubstrate) vs. the bottom frames of FIG. 5B (uncoated fibroussubstrate). The quality of ink dots in various known printingtechnologies, and in direct aqueous inkjetting technologies inparticular, may vary more substantially with the type of printingsubstrate.

A reference inkjet ink, along with a reference printing method therefor,may be used to structurally define the various optical properties of inkdot constructions on a substrate to substrate basis, by normalizingthose properties to the printing substrate.

The reference ink contained 15% Basacid Black X34 liquid (BASF), 60%propylene glycol, and 25% distilled water. The dye was added to amixture of water and propylene glycol. After 5 minutes of stirring, theink was passed through a 0.2 micrometer filter. The reference inkcomposition is simple, and the components are generic, or at leastcommercially available. In the event that Basacid Black X34 liquid(BASF) is not available, a similar black inkjet colorant may besubstituted therefor. In any event, a supply of the reference ink may beobtained from Landa Corporation, POB 2418, Rehovot 7612301, Israel.

The reference ink was printed using a FUJIFILM Dimatix MaterialsPrinter, DMP-2800, equipped with a 10 pL print head, DMC-11610. Theprinting parameters were set as follows:

-   Ink Temperature: 25° C.-   Substrate Temperature: 25° C.-   Firing Voltage: 25 V-   Meniscus Setpoint: 2.0 (inches of water)-   Distance from the print head to the substrate: 1 mm.

The printing apparatus is commercially available. If unavailable, afunctionally equivalent (or substantially functionally equivalent)printer may be used. Alternatively, such printing apparatus may beavailable courtesy of Landa Corporation, POB 2418, Rehovot 7612301,Israel.

The reference inkjet ink was prepared and printed onto various printingsubstrates, as described hereinabove. The printed dots were subjected toimage processing for characterization of roundness and convexity.

FIG. 5E-1 provides comparative bar graphs of the deviation fromroundness for ink dots produced according to some embodiments of thepresent invention, vs. ink dots produced using the above-describedreference ink formulation and printing method. The comparative study wasconducted using 10 fibrous substrates of varying physical and chemicalproperties; these included both coated and uncoated substrates. Thesubstrates are identified and partially characterized in Table 2, whichfurther provides the deviation from roundness results of the comparativestudy, for each of the 10 fibrous substrates.

It is manifest that for all fibrous substrates, (commodity) coated anduncoated, the inventive dot constructions exhibit lower deviations fromroundness (ER−1 or DR_(dot)). The highest value of DR_(dot), 0.19,obtained for an uncoated substrate (Hadar Top), is still less than ⅕ ofthe lowest roundness deviation value of the reference ink dots (RDR),1.16, obtained for a coated “silk” substrate (Sappi Magno Satin).

TABLE 2 Deviation From Roundness Inv./Ref. Reference Inventive RatioDELTA GSM Dots Dots (DR_(dot)/RDR (RDR − # Substrate name (g/m²) Type(RDR) (DR_(dot)) or “K1”) DR_(dot)) 1 Iggesund Silk 300 300 Coated 2.850.063 0.022 2.78 2 Arjowiggins (Dalum) 170 Uncoated 3.05 0.124 0.0412.92 Cyclus 3 Invercote Creato 300 300 Coated (SBS, C2S) 2.57 0.0520.020 2.52 4 Arjowiggins Gloss 170 Coated Gloss, Recycled 1.49 0.0350.024 1.45 5 Dalum Gloss recycled 170 Coated Gloss, Recycled 1.42 0.0730.051 1.35 6 Sappi Magno Satin 170 Coated Silk 1.16 0.049 0.043 1.11 7Sappi Magno Star 250 Coated Gloss 1.51 0.032 0.021 1.47 8 Invercote G300 Coated (SBS, C1S) 2.41 0.087 0.036 2.33 9 Stora Enso 275 Coated(WLC, C1S) 1.44 0.044 0.031 1.39 10 Hadar Top 170 Uncoated Offset 2.640.187 0.071 2.45

On a per-substrate basis, the difference between DR_(dot) and RDR areeven more pronounced. The ratio of DR_(dot)/RDR, also referred to as thecoefficient “K1”, ranges from about 0.02 to about 0.07, corresponding toa factor of 14:1 to 50:1, on a per-substrate basis.

Thus, according to some embodiments of the present invention,coefficient K1 may be at most 0.25, at most 0.22, at most 0.20, at most0.17, at most 0.15, at most 0.12, at most 0.10, at most 0.09, or at most0.08, for both coated (commodity-coated) and uncoated substrates, and insome cases, at most 0.070, at most 0.065, at most 0.060, at most 0.055,at most 0.050, at most 0.045, or at most about 0.04.

Coefficient K1 may be at least 0.010, at least 0.015, at least 0.180, orat least about 0.020. In some cases, coefficient K1 may be at least0.03, at least 0.04, at least 0.05, at least 0.06, at least about 0.07,at least about 0.075, at least about 0.08, at least about 0.09, at leastabout 0.10.

For coated substrates, coefficient K1 may be at most 0.070, at most0.065, at most 0.060, or at most 0.055, and in some cases, at most0.050, at most 0.045, at most 0.040, at most 0.035, at most 0.030, atmost 0.025, or at most 0.022.

FIG. 5E-2 provides comparative bar graphs of ink dot convexity of theink dot constructions of FIG. 5E-1, for each of the 10 above-describedfibrous substrates. Table 3 provides the non-convexity results of thecomparative study, for each of the 10 fibrous substrates.

TABLE 3 Non-Convexity (1-CX) Inv./Ref. Reference Inventive Ratio DELTAGSM Dots Dots (DC_(dot)/RDC (Ref. − # Substrate name (g/m²) Type (RDC)(DC_(dot)) or “K”) Inv.) 1 Iggesund Silk 300 300 Coated 0.053 0.00580.109 0.048 2 Arjowiggins (Dalum) 170 Uncoated 0.107 0.0077 0.072 0.099Cyclus 3 Invercote Creato 300 300 Coated (SBS, C2S) 0.047 0.0050 0.1070.042 4 Arjowiggins Gloss 170 Coated Gloss, Recycled 0.026 0.0043 0.1670.022 5 Dalum Gloss recycled 170 Coated Gloss, Recycled 0.044 0.00470.106 0.040 6 Sappi Magno Satin 170 Coated Silk 0.035 0.0049 0.139 0.0307 Sappi Magno Star 250 Coated Gloss 0.044 0.0042 0.096 0.040 8 InvercoteG 300 Coated (SBS, C1S) 0.047 0.0073 0.157 0.039 9 Stora Enso 275 Coated(WLC, C1S) 0.033 0.0049 0.147 0.029 10 Hadar Top 170 Uncoated Offset0.239 0.0096 0.040 0.143It is manifest that for all fibrous substrates, (commodity) coated anduncoated, the inventive dot constructions exhibit lower non-convexities(1−CX or DC_(dot)). The highest value of DC_(dot), obtained for anuncoated substrate (Hadar Top), 0.010, is still less than ⅖ of thelowest roundness deviation value of the reference ink dots (RDR),obtained for a coated gloss substrate (Arjowiggins Gloss), 0.026.

On a per-substrate basis, the difference between DC_(dot) and RDC areeven more pronounced. The ratio of DC_(dot)/RDC, also referred to as thecoefficient “K”, ranges from about 0.04 to about 0.17, corresponding toa factor of 6:1 to 25:1, on a per-substrate basis.

Thus, according to some embodiments of the present invention,coefficient K may be at most 0.35, at most 0.32, at most 0.30, at most0.27, at most 0.25, at most 0.22, at most 0.20, at most 0.19, or at most0.18, for both coated (commodity-coated) and uncoated substrates.Coefficient K may be at least 0.010, at least 0.02, at least 0.03, or atleast about 0.04. In some cases, coefficient K may be at least 0.05, atleast 0.07, at least 0.10, at least 0.12, at least 0.15, at least 0.16,at least 0.17, at least 0.18, at least 0.19, or at least about 0.20.

For uncoated substrates, coefficient K may be at most 0.15, at most0.12, at most 0.10, at most 0.09, at most 0.08, or at most 0.075, and insome cases, at most 0.070, at most 0.065, at most 0.060, or at most0.055, and in some cases, at most 0.050, at most 0.045, or at most0.040.

Coefficient K may be at least 0.020, at least 0.03, at least 0.04, atleast 0.06, at least 0.07, or at least about 0.08. In some cases,particularly for various commodity-coated substrates, coefficient K maybe at least 0.10, at least about 0.12, at least about 0.14, at leastabout 0.16, at least about 0.18, or at least about 0.20.

Field of View

The ink dots in the ink dot constructions of the present invention mayexhibit consistently good shape properties (e.g., convexity, roundness,edge raggedness, and the like), irrespective, to a large degree, of theparticular, local topographical features of the substrate, andirrespective, to some degree, of the type of printing substrate (coatedor uncoated printing substrates, plastic printing substrates, etc.). Thequality of ink dots in various known printing technologies, and indirect aqueous inkjetting technologies in particular, may varyappreciably with the type of printing substrate, and with theparticular, local topographical features of the substrate. It will bereadily appreciated that, by way of example, when an ink drop is jettedonto a particularly flat local contour having a relatively homogeneoussubstrate surface (such as a broad fiber), the ink dot obtained maydisplay significantly better shape properties, with respect to theother, or average ink dots disposed elsewhere on the substrate.

Using a more statistical approach, however, may better distinguishbetween the inventive ink dot constructions with respect to ink dotconstructions of the art. Thus, in some embodiments of the presentinvention, the ink dot constructions may be characterized as a pluralityof ink dots disposed on the substrate, within a representative field ofview. Assuming the characterization of the dot is obtained through imageprocessing, a field of view contains a plurality of dot images, of whichat least 10 dot images are suitable for image processing. Both the fieldof view and the dot images selected for analysis are preferablyrepresentative of the total population of ink dots on the substrate(e.g., in terms of dot shape).

As used herein in the specification and in the claims section thatfollows, the term “geometric projection” refers to an imaginarygeometric construct that is projected onto a printed face of a printingsubstrate.

As used herein in the specification and in the claims section thatfollows, the term “distinct ink dot” refers to any ink dot or ink dotimage, at least partially disposed within the “geometric projection”,that is neither a “satellite”, nor an overlapping dot or dot image.

As used herein in the specification and in the claims section thatfollows, the term “mean deviation”, with respect to the roundness,convexity, and the like, of a plurality of “distinct ink dots”, refersto the sum of the individual distinct ink dot deviations divided by thenumber of individual distinct ink dots.

Procedure

A printed sample, preferably containing a high incidence of single inkdots, is scanned manually on the LEXT microscope, using a ×20magnification to obtain a field that includes at least 10 single dots ina single frame. Care should be taken to select a field whose ink dotquality is fairly representative of the overall ink dot quality of theprinted sample.

Each dot within the selected frame is analyzed separately. Dots that are“cleaved” by the frame margins (which may be considered a squaregeometric projection) are considered to be part of the frame, and areanalyzed. Any satellites and overlapping dots are excluded from theanalysis. A “satellite” is defined as an ink dot whose area is less than25% of the average dot area of the dots within the frame, for frameshaving a generally homogeneous dot size, or as an ink dot whose area isless than 25% of the nearest adjacent dot, for non-homogeneous frames.

Each distinct ink dot is subsequently magnified with a ×100 zoom, andimage processing may be effected according to the procedure providedhereinabove with respect to the convexity and roundness procedures.

Results

FIG. 5F-1 provides a magnified view of a small field of ink dots on acommodity-coated fibrous substrate (Arjowiggins coated recycled gloss,170 gsm), the field produced using a commercially available aqueous,direct inkjet printer. Ink image A is a satellite, and is excluded fromthe analysis. Dot B is cleaved by the frame margin, and is included inthe analysis (i.e., the full ink dot is analyzed). Tail or projection Cis considered to be part of the ink dot disposed to its left. Thus, thefield contains only 6 ink dots for image processing.

FIG. 5F-2 provides a magnified view of a field of an ink dotconstruction according to the present invention, in which thecommodity-coated substrate is identical to that of FIG. 5F-1. Ink imageD, by way of example, is a satellite, and is excluded from the analysis.Thus, the field contains 12 ink dots for image processing.

It is manifest from a comparison of the figures that the field of inkdots displayed in FIG. 5F-1 exhibits superior dot shape and average dotshape, with respect to the field of ink dots displayed in FIG. 5F-2.

FIG. 5G-1 provides a magnified view of a field of ink dots or splotcheson an uncoated fibrous substrate (Hadar Top uncoated-offset 170 gsm),the field produced using a commercially available aqueous, direct inkjetprinter. At higher magnification, it became evident that dots E and Fare distinct individual dots. While several splotches are reasonablyround and well-formed, most of the splotches display poor roundness andconvexity, have poorly-defined edges, and appear to contain multiple inkcenters that are associated or weakly associated.

By sharp contrast, FIG. 5G-2 provides a magnified view of a field of anink dot construction according to the present invention, in which theuncoated substrate is identical to that of FIG. 5G-1. Each ink dotexhibits good roundness and convexity, and has well-defined edges.Moreover, each ink dot is disposed on top of the coarse, uncoatedfibrous substrate.

Deviation from roundness and non-convexity data for each of the fieldsis provided in Tables 4A-4D.

The fields of the ink dot construction according to the presentinvention exhibited (average) non-convexities of 0.003 for theArjowiggins coated substrate, and 0.013 for the Hadar Top uncoatedsubstrate. These average values are highly similar to thenon-convexities exhibited by individual ink dots of the presentinvention on these substrates (0.004 and 0.010, respectively).Similarly, the fields of the ink dot construction according to thepresent invention exhibited (average) deviations from roundness of 0.059for the Arjowiggins coated substrate, and 0.273 for the Hadar Topuncoated substrate. These average values are higher than, but fairlysimilar to, the deviations from roundness exhibited by individual inkdots of the present invention on these substrates (0.026 and 0.239,respectively). As articulated hereinabove, and as is manifest to the eyefrom FIGS. 5F-2 and 5G-2, ink dots in the ink dot constructions of thepresent invention tend to exhibit consistently good shape properties(such as convexity and roundness), largely irrespective of theparticular, local topographical features of the substrate.

These exemplary results have been confirmed on several additionalfibrous substrates, both commodity-coated and uncoated.

For all tested commodity-coated fibrous substrates, fields of the inkdot construction according to the present invention exhibited a meannon-convexity of at most 0.05, at most 0.04, at most 0.03, at most0.025, at most 0.020, at most 0.015, at most 0.012, at most 0.010, atmost 0.009, or at most 0.008.

For all tested uncoated fibrous substrates, fields of the ink dotconstruction according to the present invention exhibited a meannon-convexity of at most 0.085, at most 0.07, at most 0.06, at most0.05, at most 0.04, at most 0.03, at most 0.025, at most 0.020, at most0.018, or at most 0.015.

TABLE 4 Dot index ER-1 1-CX COATED SUBSTRATE A Prior Art Ink DotConstruction (FIG. 5F-1) 1 0.567 0.038 2 0.946 0.134 3 1.933 0.132 40.675 0.048 5 0.565 0.030 6 0.972 0.130 Average 0.943 0.085 B InventiveInk Dot Construction (FIG. 5F-2) 1 0.049 0.003 2 0.070 0.004 3 0.0490.003 4 0.060 0.003 5 0.050 0.003 6 0.054 0.003 7 0.066 0.003 8 0.0790.004 9 0.054 0.004 10 0.057 0.005 11 0.050 0.002 12 0.068 0.004 Average0.059 0.003 UNCOATED SUBSTRATE C Prior Art Ink Dot Construction (FIG.5G-1) 1 5.410 0.225 2 3.878 0.319 3 4.025 0.311 4 1.415 0.159 5 2.8460.297 6 3.566 0.283 7 1.584 0.145 8 4.051 0.285 Average 3.347 0.253 DInventive Ink Dot Construction (FIG. 5G-2) 1 0.277 0.016 2 0.151 0.007 30.212 0.009 4 0.302 0.017 5 0.323 0.020 6 0.355 0.015 7 0.316 0.018 80.196 0.007 9 0.274 0.008 10 0.307 0.021 11 0.247 0.010 12 0.319 0.011Average 0.273 0.013

In some embodiments, the field non-convexity is at least 0.0005, atleast 0.001, at least 0.002, at least 0.003, or at least about 0.004. Insome cases, and particularly for uncoated fibrous substrates, the fieldor mean non-convexity may be at least 0.05, at least 0.07, at least0.10, at least 0.12, at least 0.15, at least 0.16, at least 0.17, or atleast 0.18.

For all tested commodity-coated fibrous substrates, fields of the inkdot construction according to the present invention exhibited a meandeviation from roundness of at most 0.60, at most 0.50, at most 0.45, atmost 0.40, at most 0.35, at most 0.30, at most 0.25, at most 0.20, atmost 0.17, at most 0.15, at most 0.12, or at most 0.10.

For all tested uncoated fibrous substrates, fields of the ink dotconstruction according to the present invention exhibited a meandeviation from roundness of at most 0.85, at most 0.7, at most 0.6, atmost 0.5, at most 0.4, at most 0.35, at most 0.3, at most 0.25, at most0.22, or at most 0.20.

In some embodiments, the mean deviation from roundness is at least0.010, at least 0.02, at least 0.03, or at least about 0.04. In somecases, the deviation from roundness may be at least 0.05, at least 0.07,at least 0.10, at least 0.12, at least 0.15, at least 0.16, at least0.17, or at least 0.18.

While the above-described non-convexity and deviation from roundnessvalues are for fields having at least 10 dots suitable for evaluation,they further apply to fields having at least 20, at least 50, or atleast 200 of such suitable dots. Moreover, the inventors have found thatthe distinction between both the non-convexity values and deviation fromroundness values of the inventive ink dot constructions vs. theprior-art ink dot constructions becomes even more statisticallysignificant with increasing field size.

For all tested plastic substrates, described in greater detailhereinbelow, the fields of the ink dot construction according to thepresent invention exhibited a mean non-convexity of at most 0.075, atmost 0.06, at most 0.05, at most 0.04, at most 0.03, at most 0.025, atmost 0.020, at most 0.015, at most 0.012, at most 0.010, at most 0.009,or at most 0.008; the fields of the ink dot construction according tothe present invention exhibited a mean deviation from roundness of atmost 0.8, at most 0.7, at most 0.6, at most 0.5, at most 0.4, at most0.35, at most 0.3, at most 0.25, at most 0.20, at most 0.18, or at most0.15. Smooth plastics, such as atactic polypropylene and variouspolyesters, exhibited a mean deviation from roundness of at most 0.35,at most 0.3, at most 0.25, at most 0.20, at most 0.18, at most 0.15, atmost 0.12, at most 0.10, at most 0.08, at most 0.06, at most 0.05, atmost 0.04, or at most 0.035.

Plastic Substrates

FIGS. 5H-1-5H-3 provide magnified top views of ink dot constructionsaccording to the present invention, in which an ink dot is printed oneach of various exemplary plastic printing substrates, includingbiaxially oriented polypropylene—BOPP (FIG. 5H-1); anti-static polyester(FIG. 5H-2); and atactic polypropylene (FIG. 5H-3).

On all of the various plastic printing substrates used, and as shown inexemplary fashion in FIGS. 5H-1-5H-3, the ink dots of the presentinvention exhibited superior optical and shape properties, includingroundness, convexity, edge raggedness, and surface roughness.

FIG. 5H-4 provides a magnified top view of an ink dot printed on apolyester substrate, in accordance with the present invention. FIG. 5H-4further provides a cross-sectional representation showing the surfaceroughness of the ink dot and substrate. The ink dot has a height ofabout 600 nm. The deviation in height is less than ±50 nm over themiddle 80% of the dot diameter, and less than ±25 nm over the middle 60%of the dot diameter.

Exemplary deviations from roundness and non-convexities are provided inTable 5.

TABLE 5 Substrate Type ER-1 1-CX BOPP 0.1442 0.0097 Anti-Static 0.02880.0016 Polyester Atactic 0.0299 0.0020 Polypropylene

The non-convexity, or deviation from convexity for ink dots printed on awide variety of plastic printing substrates, was at most 0.020, at most0.018, at most 0.016, at most 0.014, at most 0.012, or at most 0.010. Atleast some of the ink dots, on all these substrates, including BOPP,exhibited non-convexities of at most 0.008, at most 0.006, at most0.005, at most 0.004, at most 0.0035, at most 0.0030, at most 0.0025, orat most 0.0020. On the polyester and the atactic polypropylenesubstrates, typical ink dots exhibited non-convexities of at most 0.006,at most 0.004, at most 0.0035, and even more typically, at most 0.0030,at most 0.0025, or at most 0.0020.

On all plastic substrates tested, individual ink dots in the ink dotconstructions according to the present invention exhibited a typicaldeviation from roundness of at most 0.8, at most 0.7, at most 0.6, atmost 0.5, at most 0.4, at most 0.35, at most 0.3, at most 0.25, at most0.20, at most 0.18, or at most 0.15. On various smooth plastics, such asatactic polypropylene and various polyesters, individual ink dotsexhibited a typical deviation from roundness of at most 0.35, at most0.3, at most 0.25, at most 0.20, at most 0.18, at most 0.15, at most0.12, at most 0.10, at most 0.08, at most 0.06, at most 0.05, at most0.04, or at most 0.035.

FIGS. 5H-5-5H-7 each provide a magnified view of a field having an inkdot construction according to the present invention, each fieldcontaining ink dots printed onto a respective plastic substrate. In FIG.5H-5, the substrate is anti-static polyester; in FIG. 5H-6, thesubstrate is polypropylene (BOPP WBI 35 micron (Dor, Israel)); in FIG.5H-7, the printing substrate is atactic polypropylene. In all of thesefields, each ink dot exhibits good roundness and convexity, haswell-defined edges, and is disposed on top of the particular plasticsubstrate. The ink dots of inventive ink dots-on-plastic constructionsmay closely resemble the ink dots on commodity-coated substrates,particularly with regard to the roundness, convexity, edge raggedness,and other optical shape properties. For a wide variety of plasticsubstrates, the inventive ink dots-on-plastic constructions displayoptical shape properties (e.g., deviation from roundness, non-convexity)that equal, or surpass, those of the commodity-coated substrates.

Optical Uniformity

The original ink film images provided in FIGS. 5A and 5B are notoptically uniform. Generally, the ink film images disposed on uncoatedpaper are less optically uniform than the corresponding ink film imagesdisposed on coated paper.

Furthermore, it can be observed that the inventive ink dots exhibitsuperior optical uniformity in comparison with the various prior-art inkforms. This appears to hold for both uncoated and coated printedsubstrates. That which is readily observed by the human eye may bequantified using image-processing techniques. The method of measuringink dot uniformity is provided below.

Optical Uniformity Measurement

The dot images are loaded to the ImageXpert Software, preferably usingthe statistical rules provided hereinabove. Each image is loaded in eachof the Red, Green and Blue channels. The channel selected for the imageprocessing is the channel exhibiting the highest visible details, whichinclude the dot contour and color variance within the dot area, and thesubstrate surface fibrous structure. For example, the Red channel istypically most suitable for a cyan dot, while the Green channel istypically most suitable for a magenta dot.

For each of the selected dots, a line profile (preferably 3 lineprofiles for each of the at least 10 most representative dots) ismeasured across the dot area, crossing through the center of the dot.Since the line profile is measured on a single channel, gray values(0-255, non color values) are measured. The line profiles are takenacross the center of the dot and cover only the inner two thirds of thedot diameter, to avoid edge effects. The standard for sampling frequencyis about 8 optical measurements along the line profile (8 measured grayvalues evenly spaced along each micrometer, or 125 nanometers+/−25nanometers per measurement along the line profile), which was theautomatic frequency of the ImageXpert Software, and which was found tobe suitable and robust for the task at hand.

The standard deviation (STD) of each of the line profiles is computed,and multiple line-profile STDs for each type of printed image areaveraged into a single value.

FIGS. 6A-1 to 6J-2 provide images of ink splotches or dots obtainedusing various printing technologies, and optical uniformity profilestherefor. More specifically, FIGS. 6A-1 to 6E-1 provide ink dot imagesdisposed on uncoated paper, for the following printing technologies: HPDeskJet 9000 (FIG. 6A-1); Digital press: HP Indigo 7500 (FIG. 6A-2);Offset: Ryobi 755 (FIG. 6A-3); Xerox DC8000 (FIG. 6A-4); and for anembodiment of the inventive printing technology (FIG. 6A-5). Similarly,FIGS. 6F-1 to 6J-1 provide ink dot images disposed on commodity coatedpaper, for those printing technologies.

FIGS. 6A-2 to 6J-2 respectively provide a graph plotting the (non-color)gray relative value as a function of the position on the line passingthrough the center of the ink dot image, for each of the ink dot imagesprovided by FIGS. 6A-1 to 6E-1 (on uncoated paper), and by FIGS. 6F-1 to6J-1 (on coated paper). A relatively flat linear profile for aparticular ink dot image indicates high optical uniformity along theline.

The STD of each of the line profiles of each type of printed image isprovided in Table 6, for both uncoated and coated substrates. Theresults would appear to confirm that the ink dots disposed on theuncoated fibrous printing substrates exhibit poorer uniformity withrespect to the corresponding ink dots disposed on the coated fibrousprinting substrates.

Moreover, for uncoated substrates, the line profile of the inventive inkfilm produced by the inventive system and process had an STD of 4.7,which compares favorably to the STDs achieved using the various priorart technologies (13.7 to 19.1). For coated substrates, the line profileof the inventive ink dot produced by the inventive system and processhad an STD of 2.5, which compares favorably, though less strikingly so,to the STDs achieved using the various prior art technologies (4 to11.6).

When comparing between films or dots on coated papers, the average ofeach of the standard deviations (STD) of the dot profiles of the presentinvention was always below 3. More generally, the STD of the dotprofiles of the present invention is less than 4.5, less than 4, lessthan 3.5, less than 3, or less than 2.7.

TABLE 6 STANDARD DEVIATION Uncoated Coated HP DeskJet 9000 19.1 4 HPIndigo 7500 13.7 11.6 Offset: Ryobi 755 18.6 5.75 Xerox DC8000 15.4 7Inventive System 4.7 2.5

By sharp contrast, the STD of the offset Dot Uniformity profile was5.75, and the STD of the LEP (Indigo) Dot Uniformity profile was 11.6.

Thus, the STD values for the dots of the present invention aremanifestly differentiated from the STD values of the exemplary printeddots of the prior art, both on coated and uncoated papers.

In comparing between films or dots on uncoated papers, the standarddeviation (STD) of the dot profiles of the present invention was alwaysbelow 5. More generally, the STD of the dot profiles of the presentinvention is less than 10, less than 8, less than 7, or less than 6.

Because, as noted above, ink images may contain an extremely largeplurality of individual or single ink dots (at least 20, at least 100,at least 1,000, at least 10,000, or at least 100,000), it may bemeaningful to statistically define the inventive ink dot constructionswherein at least 10%, at least 20%, or at least 30%, and in some cases,at least 50%, at least 70%, or at least 90%, of the inventive ink dots(or inventive single-drop ink dots), disposed on any uncoated or coated(or commodity-coated) fibrous substrate, exhibit the above-mentionedstandard deviations for uncoated papers and for commodity-coated papers.

Optical Density

Ink formulations containing a 1:3 ratio of pigment (Clariant HostajetBlack O-PT nano-dispersion) to resin were prepared, according to Example6. The formulations were applied to Condat Gloss® coated paper (135 gsm)using various coating rods yielding wet layers having a characteristicthickness of 4-50 micrometers.

The above-provided formulation contains approximately 9.6% ink solids,of which 25% is pigment, and about 75% is resin, by weight. In all ofthe tests, the ratio of resin to pigment was maintained at 3:1. The inksolids fraction in the ink formulations varied between 0.05 and 0.12, byweight (5% to 12%). Drawdown was performed in standard fashion, directlyonto the paper. The thickness of each ink film obtained was calculated.

Optical density was measured with an X-Rite® 528 Spectro-densitometer,using status “T” mode, absolute. The results are provided in Table 7.FIG. 12 provides the optical density points obtained, along with afitted curve (the lowermost curve) of the optical density achieved as afunction of film thickness. Although we do not know the formulation tobe a prior-art formulation, the fitted curve may represent the opticaldensity capabilities of the prior art.

TABLE 7 Mayer Rod Ink Film Size Ink Solids Thickness Optical (μm)Fraction (μm) Density 50 0.096 4.80 2.35 24 0.096 2.30 2.10 12 0.0961.15 1.85 6 0.096 0.58 1.40 4 0.096 0.38 1.10 12 0.050 0.60 1.40 120.075 0.90 1.58 12 0.120 1.44 2.00

The optical density of the inventive ink film constructions may be atleast 5%, at least 7%, at least 10%, at least 12%, at least 15%, atleast 18%, at least 20%, at least 22%, at least 25%, at least 28%, atleast 30%, at least 35%, or at least 40% higher than any of the opticaldensity points obtained and plotted in FIG. 12, and/or higher than anypoint on the fitted curve represented by the function:OD _(baseline)=0.5321425673+1.87421537367*H _(film)−0.8410126431754*(H_(film))²+0.1716685941273*(H _(film))³−0.0128364454332*(H _(film))⁴wherein:

-   OD_(baseline) is the optical density provided by the fitted curve,    and-   H_(film) is the average thickness or average height of the ink film    disposed on a printing substrate such as a fibrous printing    substrate.

The exemplary curves disposed above the fitted curve in FIG. 12 areoptical density curves of the inventive ink film construction, in whichthe optical density is 7% higher or 15% higher, respectively, thanOD_(baseline).

In absolute terms, the optical density of the inventive ink filmconstructions (OD_(invention)) may be at least 0.08, at least 0.10, atleast 0.12, at least 0.15, at least 0.18, at least 0.20, at least 0.25,at least 0.30, at least 0.35, or at least 0.40 higher than any of theoptical density points obtained and plotted in FIG. 12, and/or higherthan any point on the fitted curve represented by the above-providedfunction (OD_(baseline)). In addition, for a film thickness of at least1.5 microns, OD_(invention) may be at least 0.45, at least 0.50, atleast 0.55, at least 0.60, at least 0.70, at least 0.80, at least 0.90,at least 1.00, at least 1.10, or at least 1.25 higher than any of theoptical density points obtained and plotted in FIG. 12, and/or higherthan any point on the fitted curve represented by the above-providedfunction.

FIG. 13 provides the optical density measurements of FIG. 12, plotted asa function of pigment content or calculated average pigment thickness(T_(pig)). The optical densities (Y-axis) of FIG. 13 are identical tothose shown in FIG. 12, but the variable of the X-axis is pigmentcontent or calculated average pigment thickness, instead of averagemeasured or calculated ink film thickness. Thus,OD _(baseline)=0.5321425673+7.49686149468*T _(pig)−3.3640505727016*(T_(pig))²+0.6866743765092*(T _(pig))³−0.0513457817328*(T _(pig))⁴

In the case of black pigments such as black pigments including orsubstantially consisting of carbon black, the calculated average pigmentthickness may roughly equal the ink solids thickness multiplied by theweight fraction of the pigment within the ink solids fraction (by way ofexample, in the above-referenced formulation, the weight fraction of thepigment is 0.25).

The optical density of the inventive ink film constructions may be atleast 5%, at least 7%, at least 10%, at least 12%, at least 15%, atleast 18%, at least 20%, at least 22%, at least 25%, at least 28%, atleast 30%, at least 35%, or at least 40% higher than any of the opticaldensity points obtained and plotted in FIG. 13, and/or higher than anypoint on the fitted curve of OD_(baseline) as a function of thecalculated average pigment thickness.

In absolute terms, the optical density of the inventive ink filmconstructions (OD_(invention)) may be at least 0.08, at least 0.10, atleast 0.12, at least 0.15, at least 0.18, at least 0.20, at least 0.25,at least 0.30, at least 0.35, or at least 0.40 higher than any of theoptical density points obtained and plotted in FIG. 13, and/or higherthan any point on the fitted curve represented by the above-providedfunction (OD_(baseline)). In addition, for a film thickness of at least1.5 microns, OD_(invention) may be at least 0.45, at least 0.50, atleast 0.55, at least 0.60, at least 0.70, at least 0.80, at least 0.90,at least 1.00, at least 1.10, or at least 1.25 higher than any of theoptical density points obtained and plotted in FIG. 13, and/or higherthan any point on the fitted curve of OD_(baseline) as a function of thecalculated average pigment thickness.

Color Gamut Volume

The color gamut of a particular printing technology may be defined asthe sum total of all colors that the printing technology can reproduce.While color gamuts may be represented in various ways, a full colorgamut is generally represented in a three-dimensional color space.

ICC (International Color Consortium) profiles are often utilized bycommercially available software to evaluate color gamut volume.

ISO Standard 12647-2 (‘Amended Standard’ version), which is incorporatedby reference for all purposes as if fully set forth herein, relates tovarious printing parameters for offset lithographic processes, includingCIELAB coordinates, gloss, and ISO brightness for five typical offsetsubstrates.

ISO Amended Standard 12647-2 defines CIELAB coordinates of colors forthe printing sequence black-cyan-magenta-yellow, for each of the fivetypical offset substrates, and based thereupon, defines, for each ofthese substrates, a resulting color gamut of offset lithographicprinting.

In practice, the color gamut volume capabilities of the prior art maybe, at most, about 400 kilo(ΔE)³ for coated wood free paper (e.g., Type1 and possibly Type 2 of ISO Amended Standard 12647-2) utilized as asubstrate in offset lithographic printing.

The color gamut volume capabilities of the prior art may be somewhatlower for Type 3 substrates (at most about 380 kilo(ΔE)³) and for othertypes of offset lithographic printing substrates such as uncoatedpapers, e.g., various uncoated offset papers such as Type 4 and Type 5of ISO Amended Standard 12647-2. The color gamut volume capabilities ofthe prior art may be, at most, about 350 kilo(ΔE)³ for such uncoatedoffset papers.

It is assumed that the print image thickness (single dot or film)associated with these color gamut volumes is at least 0.9-1.1micrometers.

By sharp contrast, the color gamut volume of the ink film constructionsof the present invention, as determined, for example, by ICC profiles,may exceed or appreciably exceed the above-provided color gamut volumes.For each particular substrate type, the color gamut volume of theinventive ink film constructions may exceed the respective, existingcolor gamut volume capability by at least 7%, at least 10%, at least12%, at least 15%, at least 18%, at least 20%, at least 25%, at least30%, or at least 35%.

The color gamut volume of the inventive ink film constructions mayexceed the provided, respective, color gamut volume capabilities by atleast 25 kilo(ΔE)³, at least 40 kilo(ΔE)³, at least 60 kilo(ΔE)³, atleast 80 kilo(ΔE)³, at least 100 kilo(ΔE)³, at least 120 kilo(ΔE)³, atleast 140 kilo(ΔE)³, or at least 160 kilo(ΔE)³.

In absolute terms, the color gamut volume of the inventive ink filmconstructions may be characterized by color gamut volumes of at least425 kilo(ΔE)³, at least 440 kilo(ΔE)³, at least 460 kilo(ΔE)³, at least480 kilo(ΔE)³, or at least 500 kilo(ΔE)³. For Type 1 and Type 2substrates and the like, the inventive ink film constructions may befurther characterized by color gamut volumes of at least 520 kilo(ΔE)³,at least 540 kilo(ΔE)³, at least 560 kilo(ΔE)³, or at least 580kilo(ΔE)³.

Without wishing to be limited by theory, the inventors believe that theenhanced color gamut volume, as well as the enhanced optical densitydescribed hereinabove, may be at least partially, or largely,attributable to the lamination of the inventive ink film onto a topsurface of the printing substrate. Because the form of the film may belargely determined prior to the transfer to the substrate, the film maybe integrally transferred from the ITM to the substrate. This integralcontinuous unit may be substantially devoid of solvent, such that theremay be no penetration of any kind of material from the blanket into, orbetween, substrate fibers. The integral film may form a laminated layerdisposed entirely above the top surface of the fibrous printingsubstrate.

The inventive ink film constructions may achieve the various statedcolor gamut volumes, not only within the 0.9-1.1 micrometer filmthickness range, but, surprisingly, at average film thicknesses orheights that are lower or appreciably lower than the 0.9-1.1 micrometerrange. The inventive ink film constructions may be characterized bythese color gamut volumes for ink film thicknesses of less than 0.8 μm,less than 0.7 μm, less than 0.65 μm, less than 0.6 μm, less than 0.55μm, less than 0.5 μm, less than 0.45 μm, or less than 0.4 μm.

The inventive ink film constructions may also achieve the various statedcolor gamut volumes at average film thicknesses that are at most 4micrometers, at most 3.5 μm, at most 3 μm, at most 2.6 μm, at most 2.3μm, at most 2 μm, at most 1.7 μm, at most 1.5 μm, at most 1.3 μm, or atmost 1.2 μm.

Furthermore, the inventive ink film constructions may also achieve fullcoverage of the color gamuts defined by the above-referenced ISOStandard, within any of the film thickness ranges described hereinabove.

A new standard under development, ISO Standard 15339 is provided inTable 8.

TABLE 8 Reference Volume printing ISO 15339 condition Name Typical UsedE(CIELAB)³ 1 Universal Newsprint, small gamut, 100812.3 ColdsetNewsPrinting using coldset (23% Pantones) offset, flexography, letterpress,etc. 2 Universal Improved newsprint, 184483.3 HeatsetNews moderategamut, (32% Pantones) Printing using heatset or similar technology 3Universal Utility printing on a 176121.3 PremUncoated matt uncoatedpaper (31% Pantones) 4 Universal General printing on 262646.2 SuperCalsuper-calendared paper (39% Pantones) 5 Universal Magazine publication345892.2 PubCoated (47% Pantones) 6 Universal Large gamut, Printing398593.1 PremCoated using sheet-fed offset, (52% Pantones) gravure 7Universal Digital printing and 515753.2 Extra Large potentially otherlarge (62% Pantones) gamut printing processes

Color gamut prints were made using Dimatix SAMBA single pass inkjetprint heads having a nominal resolution of 1200 dpi and providing anaverage drop volume of 9 pL.

Ink in the print head was maintained 22° C., the blanket was maintainedat 70° C. Manual drying was effected at about 450° C. at a volume flowof 16 CFM. The transfer temperature was about 130° C. Ink formulationswere prepared substantially as described above with respect to Examples2, 5, 8 and 9.

For each run, 170 patches of different color combinations were printedand measured using a spectrophotometer, to create the color gamut. Eachcolor separation was printed sequentially on a heated blanket and driedmanually for approximately 2 seconds. The order of the separations wasyellow, magenta, cyan and black. After all the separations were printed,the image was transferred to the paper by applying pressure using acylindrical weight.

Each individual color separation had a thickness of up to 600, up to650, or up to 700 nm. The total thickness was at most 2,000 nm, and onaverage, about 1,700 nm, 1,800 nm or 1900 nm. In some runs, eachindividual color separation had a thickness of up to 450, up to 500, orup to 550 nm, and the corresponding average total thickness was about1,300 nm, 1,400 nm or 1,500 nm.

All comparisons were done with normalized white, as though printed onthe same media.

The software used to create a color profile from the prints was ani1Profiler, version 1.4.2 (X-Rite® Inc., Grand Rapids, Mich.).Measurements were done using an i1Pro2 spectrophotometer (X-Rite® Inc.),and standard techniques (similar to those of the i1Profiler) were usedto plot the charts and to calculate the color gamut volume.

Abrasion Resistance

One important characteristic of printed ink films is abrasionresistance. Abrasion resistance is a property of printed ink describingthe degree to which the printed image can maintain its surface andstructural integrity under prolonged rubbing, scratching and scuffing.During shipping and handling, the exposed surface of printed ink filmsmay be appreciably abraded, thereby detracting from print quality.Consequently, a wide variety of printed products (e.g., magazines andbrochures) may require ink film constructions having superior abrasionresistance.

Abrasion resistance may typically be enhanced by using suitableformulations comprising resins having good abrasion resistanceproperties. Alternatively or additionally, special components such aswaxes and/or hard-drying oils, may be introduced to the formulation.

The introduction of waxes or oils to the ink formulation may affect theoverall attributes of the ink and may also lead to other process-relatedor print-related problems. Thus, providing the requisite abrasionresistance solely by means of abrasion resistant resins may beadvantageous in at least this respect.

The inventors have discovered that in the ink formulations and in theink film constructions of the present invention, various resins, havingrelatively poor mechanical or “bulk” abrasion resistance properties, mayadvantageously contribute to the thermo-rheological behavior of thoseink formulations, whereby at least one of: the development of the inkfilm, the transfer from the intermediate transfer member or blanket, andthe adhesion to the printing substrate, may be appreciably enhanced. Thepoor mechanical properties of the resins may include a low hardnessvalue.

The inventors have discovered that the abrasion resistance of printimages printed with inventive ink formulations containing such resins issurprisingly high with respect to the “bulk” abrasion resistanceproperties of those resins.

Abrasion resistance was measured by sweeping an abrasive block on top ofeach sample a number of times, and measuring the optical density of thesamples as compared to baseline values established for those samplesprior to the abrasive testing. The samples were placed into a TMI(Testing Machines Incorporated) ink rub tester (model #10-18-01) and adry ink rub test was performed using a 1.8 kg test block having a pieceof Condat Gloss® paper (135 gsm) disposed thereon. Optical densities ofthe samples were measured before the test and after 100 abrasion cycles.This abrasion resistance measurement procedure is recommended by the TMIInstruction Manual, and is based on ASTM procedure D5264.

By way of example: the high molecular weight polymer in Joncryl® 2178film-forming emulsion was tested for abrasion resistance, and was foundto have excellent abrasion resistance properties. An ink formulationcontaining the Joncryl® 2178 was prepared, and applied on Condat Gloss®paper (135 gsm) using a 12 micrometer coating rod. With this inkformulation, a 12 μm wet thickness approximately corresponds to a dryfilm having a film thickness of 1.2 μm. Drawdown was performed instandard fashion. The dry ink film sample was then tested for abrasionresistance. The optical density loss was only 18% after 100 abrasioncycles, which is considered an excellent result for various printingapplications.

The Joncryl® 2178 film-forming emulsion was further tested forthermo-rheological compatibility with the inventive process, and wasfound to have poor transfer properties.

A second, lower molecular weight resin (Neocryl® BT-26) was tested forabrasion resistance, and was found to have relatively poor abrasionresistance properties. As with the first resin, a second ink formulationcontaining the above-referenced resin was prepared, and applied onCondat Gloss® paper (135 gsm) using the 12 μm coating rod. The dry filmobtained, having a film thickness of about 1.2 μm, was subjected to theabove-described abrasion resistance test. The optical density loss was53% after 100 abrasion cycles, nearly three times the loss borne bysample 1.

The inventive ink formulation was further tested for thermo-rheologicalcompatibility with the inventive process, and was found to have adequatetransfer properties.

The inventors then tested this second ink formulation containing theresin having relatively poor abrasion resistance properties, in aprinting system and processing method of the present invention. Again,Condat Gloss® paper (135 gsm) was used as the printing substrate. Someof the ink film constructions produced were evaluated to assess variousprint and ink film construction properties, including abrasionresistance.

The printed substrate obtained using the second ink formulation wassubjected to an abrasion resistance test identical to that performed forthe drawdown samples. Surprisingly, the optical density loss was 16.6%,which is comparable to the abrasion resistance of the first, highlyabrasion-resistant dry ink film sample, and which is a sufficiently goodresult for a wide range of printing applications.

In another exemplary abrasion resistance test, an ink formulation wasprepared, according to the composition provided in Example 8. The inkwas applied on Condat Gloss® paper (135 gsm) using the 12 μm coatingrod. Then the ink was dried by hot air and the abrasion resistance wastested, as described above. The optical density loss was 30% after 100abrasion cycles.

In another exemplary abrasion resistance test, the above-described inkformulation was used to produce a dry film by means of the inventiveprocess. The dry film, having a thickness of about 1 micrometer, wasobtained by applying the wet ink (12 μm, as above) on a hot (130° C.)[silanol-terminated polydimethyl-siloxane] silicone blanket, drying thefilm, and transferring the dried film to Condat Gloss® paper (135 gsm).The optical density loss was 19% after 100 abrasion cycles.

Adhesive Failure

The adhesive properties of the inventive ink film constructions (interalia, Example 4) were evaluated and compared against the adhesiveproperties of ink dot or ink film constructions of the prior art. Astandard testing procedure used: quantitative ink adhesion test FTM 21of FINAT (Federation Internationale des Fabricants et Trans formateursd'Adhesifs et Thermocollants sur Papiers et Autres Supports), providedbelow.

FINAT FTM 21

Ink Adhesion—Basic

-   Scope This method allows rapid assessment of the degree of adhesion    of a printing ink or lacquer to a labelstock.-   Definition The printing ink or lacquer is applied to the substrate    and cured on the printing press or using a standard method    appropriate for the type of ink. The ink adhesion is then estimated    by the amount of ink that can be removed when adhesive tape is    applied and peeled off. The resistance of the ink to mechanical    removal is also measured by scratching the ink and by deformation    under pressure.-   Test Equipment A means of applying and curing the ink. Adhesive tape    of high peel adhesion (‘aggressive’), for example Tesa 7475 (acrylic    based), Tesa 7476 (rubber based), or 3M Scotch 810. FINAT roller to    smooth the tape over the test piece. Metal spatula. Gloves.-   Test Pieces If the required ink has not already been applied to the    substrate as part of the printing process, prepare samples for    testing by coating the ink to a uniform thickness (for example, with    a Meyer bar for low-viscosity inks) and curing the coating as    recommended by the supplier. A-4 sheets are a conveniently-sized    sample for this test. Test condition 23° C.±2° C. and 50% relative    humidity (RH)±5% RH. If practical, the test pieces should be    conditioned for at least four hours prior to testing.-   Tape test Lay the specimen on a smooth, flat, hard surface and apply    the adhesive tape, leaving a small part of the tape unfixed to the    test piece, ensuring that no air bubbles are trapped under the tape.    Using the FINAT roller, press down the tape by passing the roller    twice in each direction over the specimen, and then bend the    unattached part of the tape back on itself at an angle of 180°.    Within 20 minutes after rolling down the tape, mount the specimen in    a frame or use one hand to hold the specimen firmly, then pull the    free piece of tape towards you using the other hand: at first slowly    under constant speed, then very rapidly and accelerating. (The    faster speed is the more aggressive test). FINAT Technical Handbook    6th edition, 2001 53.

The performance of the specimen is recorded by comparison with controlsamples which have been previously measured, or by reference to thefollowing grading:

-   Grade 1 No removal of ink-   Grade 2 Slight removal of ink (<10%)-   Grade 3 Moderate removal of ink (10-30%)-   Grade 4 Severe removal of ink (30-60%)-   Grade 5 Almost complete removal of ink (>60%)

Exemplary results are provided in Table 9.

The direct (drop-on-demand) inkjet technologies displayed poor inkadhesion to the various plastic substrates. The solid ink technologyexemplified by the XEROX Phaser 8560 and the latex printing technologyexemplified by the HP Designjet Z6200 also displayed poor ink adhesionto various plastic substrates. Lithographic offset printing, gravure,and some LEP and DEP technologies displayed strong adhesive propertieson the plastic substrates tested.

With respect to various plastic substrates, including polypropylenesheets (e.g., biaxially oriented polypropylene—BOPP), polyethylenesheets, and polyethylene terephthalate sheets, the ink-filmconstructions of the present invention exhibited strong adhesiveproperties.

In some embodiments of the invention, the ink dots-on-plastic inkconstructions exhibited an adhesive failure of at most 10%, and moretypically, at most 5%, when subjected to a standard tape test (FINAT FTM21, basic ink adhesion test). In most cases, the ink dots-on-plastic inkconstructions were free or substantially free of adhesive failure whensubjected to this tape test.

TABLE 9 Printing MEAN GRADE Technology Device Substrate Type no cut withcut Variable Sleeve Offset Printing Polyethylene (web) 1 1 GravureCellulose 1 1 Flexography COMEXI Polyethylene 1.66 2 Flexography PP 1 1LEP INDIGO Shrink Sleeve Stock 1 1 Inkjet (Industrial) EFI Jetrion PP 11 DEP (LED-based) XEIKON PP 1 2 Gravure Polyethylene 1 1 LEP INDIGO WS6600 Polyethylene 1 1.66 Solid Ink XEROX Phaser 8560 PP 5 5 Solid InkXEROX Phaser 8560 Jolybar Synth. Paper 60 5 5 Solid Ink XEROX Phaser8560 100 PP 90M 5 5 Solid Ink XEROX Phaser 8560 PPX LABEL 110M 5 5 LatexHP Designjet Z6200 PP (HP Everyday Matte) 4.33 4.33 Inkjet Epson StylusSX-125 PP 5 5 Inkjet Epson Stylus SX-125 PETF-Thin 5 5 Inkjet EpsonStylus SX-125 Polyethylene 5 5 Inkjet Epson Stylus SX-125 PETF-Thick 5 5Inkjet HP DeskJet 9803 PP 5 5 Inkjet HP DeskJet 9803 PETF-Thin 5 5Inkjet HP DeskJet 9803 Polyethylene 5 5 Inkjet HP DeskJet 9803PETF-Thick 5 5 Present Invention Landa Press PP (synthetic paper) 1 1Present Invention Landa Press PP 1 1 Present Invention Landa PressPETF-Thin 1 1 Present Invention Landa Press Polyethylene 1 1 PresentInvention Landa Press PETF-Thick 1 1.33Glass Transition Temperature of the Resin

The inventors have found that in selecting resins for use within theformulations supporting the ink film constructions of the presentinvention, the softening temperature (or glass transition temperaturefor at least partially amorphous resins) may be a useful indicator ofresin suitability. Specifically, the resins used in the ink formulations(and disposed in the ink films of the present invention) may have aT_(g) below 47° C. or below 45° C., and more typically, below 43° C.,below 40° C., below 35° C., below 30° C., below 25° C., or below 20° C.

More generally, from a process standpoint, the ink formulations disposedon the ITM, after becoming devoid or substantially devoid of water, anyco-solvent, and any other vaporizable material that would be vaporizedunder process conditions, e.g., pH adjusting agents, (producing “inksolids” an “ink residue”, or the like), and/or the resins thereof, mayhave a T_(g) below 47° C. or below 45° C., and more typically, below 43°C., below 40° C., below 35° C., below 30° C., below 25° C., or below 20°C.

Thermo-Rheological Properties

The inventive process may include the heating of the ink film or image,during transport on the surface of the image transfer member, toevaporate the aqueous carrier from the ink image. The heating may alsofacilitate the reduction of the ink viscosity to enable the transferconditions from the ITM to the substrate. The ink image may be heated toa temperature at which the residue film of organic polymeric resin andcolorant that remains after evaporation of the aqueous carrier isrendered tacky (e.g., by softening of the resin).

The residue film on the surface of the image transfer member may be dryor substantially dry. The film includes the resin and the colorant fromthe ink formulation. The residue film may further include small amountsof one or more surfactants or dispersants, which are typically watersoluble at the pH of the ink (i.e., prior to jetting). The residue filmmay further include one or more plasticizers.

The ink residue film may be rendered tacky before it reaches theimpression cylinder. In this case, the film may cool at the impressionstation, by its contact with the substrate and exposure to theenvironment. The already tacky ink film may adhere immediately to thesubstrate onto which it is impressed under pressure, and the cooling ofthe film may be sufficient to reduce film adhesion to the image transfersurface to the point that the film peels away neatly from the imagetransfer member, without compromising adhesion to the substrate.

Tack (or tackiness) may be defined as the property of a material thatenables it to bond with a surface on immediate contact under lightpressure. Tack performance may be highly related to various viscoelasticproperties of the material (polymeric resin, or ink solids). Both theviscous and the elastic properties would appear to be of importance: theviscous properties at least partially characterize the ability of amaterial to spread over a surface and form intimate contact, while theelastic properties at least partially characterize the bond strength ofthe material. These and other thermo-rheological properties are rate andtemperature dependent.

By suitable selection of the thermo-rheological characteristics of theresidue film, the effect of the cooling may be to increase the cohesionof the residue film, whereby its cohesion exceeds its adhesion to thetransfer member so that all or substantially all of the residue film isseparated from the image transfer member and impressed as a film ontothe substrate. In this way, it is possible to ensure that the residuefilm is impressed on the substrate without significant modification tothe area covered by the film nor to its thickness.

Viscosity temperature sweeps—ramp and step—were performed using a ThermoScientific HAAKE RheoStress® 6000 rheometer having a TM-PE-P Peltierplate temperature module and a P20 Ti L measuring geometry (spindle).

Samples of dried ink residue having a 1 mm depth in a 2 cm diametermodule were tested. The samples were dried overnight in an oven at anoperating temperature of 100° C. A volume of sample (pellet) wasinserted into the 2 cm diameter module and softened by gentle heating.The sample volume was then reduced to the desired size by lowering thespindle to reduce the sample volume to the desired depth of 1 mm.

In temperature ramp mode, the sample temperature was allowed tostabilize at low temperature (typically 25° C. to 40° C.) before beingramped up to a high temperature (typically 160° C. to 190° C.) at a rateof approximately 0.33° C. per second. Viscosity measurements were takenat intervals of approximately 10 seconds. The sample temperature wasthen allowed to stabilize at high temperature for 120 seconds beforebeing ramped down to low temperature, at a rate of approximately 0.33°C. per second. Again, viscosity measurements were taken at intervals ofapproximately 10 seconds. Oscillation temperature sweeps were performedat a gamma of 0.001 and at a frequency of 0.1 Hz.

In the specification and in the claims section that follows, values fordynamic viscosity are quantitatively determined solely by thetemperature ramp-up and ramp-down method described hereinabove.

FIG. 7 provides ramped-down temperature sweep plots of dynamic viscosityas a function of temperature, for several dried ink formulationssuitable for the ink film construction of the present invention. Afterreaching a maximum temperature of approximately 160° C., and waiting 120seconds, the temperature was ramped down as described.

The lowest viscosity curve is that of a dried residue of an inventiveyellow ink formulation, containing about 2% pigment solids, and producedaccording to the procedure described hereinabove. At about 160° C., therheometer measured a viscosity of about 6.7·10⁶ cP. As the temperaturewas ramped down, the viscosity steadily and monotonically increased toabout 6·10⁷ cP at 95° C., and to about 48·10⁷ cP at 58° C.

The intermediate viscosity curve is that of a dried residue of aninventive cyan ink formulation, containing about 2% pigment solids, andproduced according to the procedure described hereinabove. At about 157°C., the rheometer measured a viscosity of about 86·10⁶ cP. As thetemperature was ramped down, the viscosity increased to about 187·10⁶ cPat 94° C., and to about 8·10⁸ cP at 57° C.

The highest viscosity curve is that of a dried residue of an inventiveblack ink formulation, containing about 2% pigment solids, and producedaccording to the procedure described hereinabove. At about 160° C., therheometer measured a viscosity of about 196·10⁶ cP. As the temperaturewas ramped down, the viscosity steadily and monotonically increased toabout 763·10⁶ cP at 95° C., and to about 302·10⁷ cP at 59° C.

FIG. 8 is a ramped-down temperature sweep plot of dynamic viscosity as afunction of temperature, for several dried ink formulations of thepresent invention, vs. several ink residues of prior art inkformulations. The viscosity curves of the prior art formulations arelabeled 1 to 5, and are represented by dashed lines; the viscositycurves of the inventive formulations are labeled A to E, and arerepresented by solid lines. The ink formulations of the presentinvention include the three previously described in conjunction withFIG. 7 (A=black; C=cyan; and E=yellow), and two ink formulations (“B”;“D”) containing about 2%, by weight of solids, of a magenta aqueouspigment preparation [Hostajet Magenta E5B-PT (Clariant)], along withabout 6% of various styrene-acrylic emulsions. The residues of the priorart inks were prepared from various commercially available inkjet inks,of different colors.

A magnified view of the plot of FIG. 8, for viscosities of less than36·10⁸, is provided in FIG. 9. Only the viscosity curves of theinventive formulations A to E, and that of prior-art formulation 5, maybe seen in FIG. 9.

It is evident from the plots, and from the magnitude of the viscosities,that the dried ink residues of the various prior art ink formulationsexhibit no or substantially no flow behavior over the entire measuredrange of temperatures, up to at least 160° C. The peaks observed atextremely high viscosities in some plots of the prior-art formulationswould appear to have no physical meaning. The lowest measured viscosityfor each of the prior art residue films was within a range of at least135·10⁷ cP to at least 33·10⁸ cP. The lowest value within this range,135·10⁷ cP, is well over 6 times the highest viscosity value of any ofthe residues of the inventive ink formulations, at about 160° C.

Moreover, during the ramp-down phase of the experiment, Samples 1 to 5of the prior art exhibited viscosity values that exceeded the viscositymeasured at about 160° C., and/or appear sufficiently high so as topreclude transfer of the film. In practice, the inventors of the presentinvention successfully transferred all five of the inventive ink filmsto a printing substrate, but failed to transfer any of the fiveprior-art ink films to a printing substrate, even after heating to over160° C.

The inventors have calculated the ratio of a “cold” dynamic viscosity,at least one temperature within a range of 50° C. to 85° C., to the“hot” dynamic viscosity, at least one temperature within a range of 125°C. to 160° C. The inventors believe that this ratio may be important indistinguishing between ink formulations that meet the multiplerequirements of the inventive process, and ink formulations that fail tomeet the multiple requirements of the inventive process.

Analysis of Ink Film on Printed Substrates

Basic Procedure:

Three sheets of Condat Gloss® paper (135 g/cm², B2, 750×530 mm) wereprinted on a digital press according to co-pending PCT Application No.PCT/IB2013/051716 (Agent's reference LIP 5/001 PCT), using inkformulations of the present invention (magenta, yellow, cyan and black).After 1 week, the sheets were cut into 3×3 cm pieces and introduced into300 grams of a solution containing 1% 2-amino-2-methyl-1-propanoldissolved in water able to sufficiently dissolve ink images printedusing various water-soluble inks. In this de-inking procedure, thesolution was stirred for 10 minutes at room temperature (e.g., circa 23°C.), after which the mixture was filtered through a 10 micron filter.The filtrate, mainly containing the dissolved ink and the pigmentparticles, was dried using a rotary evaporator. The filtrate residue wasthen dissolved in 5 grams of dimethyl sulfoxide (DMSO) and was thendried in an oven at 110° C. for 12 hours to yield the “recoveredresidue”.

The thermo-rheological behavior of the recovered residue obtained fromthe de-inking process was characterized by viscosity measurements in aramp-up and ramp-down temperature sweep (as described hereinabove). Theresults obtained are plotted in FIG. 10.

From FIG. 10 it appears manifest that the thermo-rheological behavior ofthe ink solids extracted from the printed images is similar to thethermo-rheological behavior characteristic of the dried ink residuesproduced by directly drying ink formulations of the present invention.It further appears manifest that the thermo-rheological behavior of therecovered residue is markedly different from the thermo-rheologicalbehavior of the dried residues of various water based ink jetformulations such as samples 1 to 5 (as shown in FIG. 8).

In another test, HP black inkjet ink (as supplied for use in HP DeskJet9803) from the cartridge was dried to form a residue. The residue wasdissolved in 5 grams of dimethyl sulfoxide (DMSO) and was then dried inan oven at 110° C. for 12 hours. 100 mg of the dry sample wasdissolved/dispersed in 0.5 ml of distilled water (or a suitable solventsuch as DMSO). After stirring, the liquid material was introduced into asilicon rubber mold. Afterwards the mold was placed on a plate (heatedto 250° C.) for 10 minutes. The dry tablet obtained was allowed to coolto room temperature, and was then subjected to a dynamic viscositymeasurement at high temperature (−190° C.). The viscosity, in cP, isplotted in FIG. 11.

The identical black inkjet ink was also printed onto several sheets ofCondat Gloss® paper using the afore-mentioned HP inkjet printer. After 1week, the sheets were cut into small pieces and introduced into a 1%solution of 2-amino-2-methyl-1-propanol in distilled water,substantially as described hereinabove. The flask was stirred for 10minutes at room temperature, after which the mixture was filteredthrough a 10 micron filter. The filtrate was dried using a rotaryevaporator. The residue was dissolved in 5 grams of dimethyl sulfoxide(DMSO) and was then dried in an oven at 110° C. for 12 hours. 100 mg ofthe dry sample was dissolved in 0.5 ml of distilled water (or a suitablesolvent such as DMSO). After stirring the liquid material was introducedinto the silicon rubber mold. Afterwards the mold was placed on a plate(heated to 250° C.) for 10 minutes. The dry tablet obtained fromde-inking of the HP inkjet printed samples was allowed to cool to roomtemperature, and was then subjected to a dynamic viscosity measurementat high temperature (˜190° C.). The viscosity, in cP, is plotted in FIG.11.

The inkjet ink residue obtained by de-inking of the HP samples exhibiteda dynamic viscosity that was similar to the dynamic viscosity exhibitedby the dried residue of the identical HP inkjet ink.

A similar test was performed for a black ink formulation of the presentinvention. Dynamic viscosity measurements were conducted at hightemperature (˜190° C.) for both the dried ink residue and the inkresidue recovered according to the above-described procedure. Theviscosity of each sample, in cP, is plotted in FIG. 11.

Again, the recovered inkjet ink residue, obtained by de-inking of theinventive ink film constructions, exhibited a dynamic viscosity that wassimilar to the dynamic viscosity exhibited by the dried residue of theidentical inventive inkjet ink.

In a more advanced procedure, 3 sheets of Condat paper (135 g/cm², B2,750×530 mm) were printed on printed on a printing system as described inco-pending PCT application of the Applicant, No. PCT/IB2013/051716,using inks as herein described, and further detailed in co-pending PCTapplication No. PCT/182013/051755 (Agent's reference LIP 11/001 PCT)using Landa inks, and subjected to the following procedure: after 1week, the sheets are cut into 3×3 cm pieces and introduced into 300grams of a solution containing 1% 2-amino-2-methyl-1-propanol dissolvedin water, which is able to sufficiently dissolve ink images printedusing various water-soluble inks. If, however, the solution remainscolorless, the water is separated off and an identical weight of a lesspolar solvent, ethanol, is introduced. Again, if the solution remainscolorless, the solvent is separated off, and an identical weight of aless polar solvent, methyl ethyl ketone, is introduced. The procedurecontinues with successfully less polar solvents: ethyl acetate, toluene,and Isopar™ (synthetic mixture of isoparaffins). After 5 hours stirringat room temperature with the most appropriate solvent, the mixture isfiltered through a 5 micrometer filter. The filtrate or filtratescontaining the dissolved ink is dried using a rotary evaporator. Theresidues are then dissolved in 5 grams of DMSO (or one of theabove-listed solvents) and dried in an oven at 110° C. for 12 hours toyield the “recovered residue”. Thermo-rheological behavior of therecovered residue is characterized and compared with a dried sample ofthe original ink, when available.

The inventors attribute the improved thermo-rheological results of thisprocedure (i.e., appreciably closer to the results obtained by directdrying of inkjet ink) to the increased dissolution of the printed ink,due to both the increased residence time and the use of additionalsolvents. Thus, this advanced procedure may advantageously be used todetermine the thermo-rheological properties of the dried ink from inkresidue recovered from printed matter such as magazines and brochures.

The absolute dynamic viscosity values of the prior-art inkjet inkresidues exceed the dynamic viscosity values of the inventive inkjet inkresidues by a factor of more than 30-40.

It is manifest that the absolute dynamic viscosity values of theprior-art and inventive inkjet ink residues may be substantiallyreproduced by measuring the absolute dynamic viscosity values of thecorresponding inkjet ink residues recovered from printed images. It isfurther manifest that this method may be utilized to characterize aninkjet ink residue by reconstituting the ink from printed substrates.

One of ordinary skill in the art will readily appreciate that other,potentially superior, procedures may be used to de-ink a printedsubstrate and produce the recovered ink residue for rheological,thermo-rheological and/or chemical analysis.

Ink Formulations and Ink Film Compositions

Among other things, the present inkjet inks are aqueous inks, in thatthey contain water, usually at least 30 wt. % and more commonly around50 wt. % or more; optionally, one or more water-miscible co-solvents; atleast one colorant dispersed or at least partly dissolved in the waterand optional co-solvent; and an organic polymeric resin binder,dispersed or at least partly dissolved in the water and optionalco-solvent.

It will be appreciated that acrylic-based polymers may be negativelycharged at alkaline pH. Consequently, in some embodiments, the resinbinder has a negative charge at pH 8 or higher; in some embodiments theresin binder has a negative charge at pH 9 or higher. Furthermore, thesolubility or the dispersability of the resin binder in water may beaffected by pH. Thus in some embodiments, the formulation includes apH-raising compound, non-limiting examples of which include diethylamine, monoethanol amine, and 2-amino-2-methyl propanol. Such compounds,when included in the ink, are generally included in small amounts, e.g.,about 1 wt. % of the formulation and usually not more than about 2 wt. %of the formulation.

It will also be appreciated that acrylic-based polymers having freecarboxylic acid groups may be characterized in terms of their chargedensity or, equivalently, the acid number, i.e., the number ofmilligrams of KOH needed to neutralize one gram of dry polymer. Thus, insome embodiments, the acrylic-based polymer has an acid number in therange of 70-144.

The ink film of the inventive ink film construction contains at leastone colorant. The concentration of the at least one colorant within theink film may be at least 2%, at least 3%, at least 4%, at least 6%, atleast 8%, at least 10%, at least 15%, at least 20%, or at least 22%, byweight of the complete ink formulation. Typically, the concentration ofthe at least one colorant within the ink film is at most 40%, at most35%, at most 30%, or at most 25%.

More typically, the ink film may contain 2-30%, 3-25%, or 4-25% of theat least one colorant.

The colorant may be a pigment or a dye. The particle size of thepigments may depend on the type of pigment and on the size reductionmethods used in the preparation of the pigments. Generally, the d₅₀ ofthe pigment particles may be within a range of 10 nm to 300 nm. Pigmentsof various particle sizes, utilized to give different colors, may beused for the same print.

The ink film contains at least one resin or resin binder, typically anorganic polymeric resin. The concentration of the at least one resinwithin the ink film may be at least 10%, at least 15%, at least 20%, atleast 25%, at least 35%, at least 40%, at least 50%, at least 60%, atleast 70%, or at least 80%, by weight.

The total concentration of the colorant and the resin within the inkfilm may be at least 10%, at least 15%, at least 20%, at least 30%, orat least 40%, by weight. More typically, however, the totalconcentration of the colorant and the resin within the ink film may beat least 50%, at least 60%, at least 70%, at least 80%, or at least 85%.In many cases, the total concentration of the colorant and the resinwithin the ink film may be at least 90%, at least 95%, or at least 97%of the ink film weight.

Within the ink film, the weight ratio of the resin to the colorant maybe at least 1:1, at least 2:1, at least 2.5:1, at least 3:1, at least4:1, at least 5:1, or at least 7:1.

The weight ratio of the resin to the colorant within the ink filmconstructions of the invention may be at most 15:1, at most 12:1, or atmost 10:1. In some applications, particularly when it is desirable tohave an ultra-thin ink film laminated onto the printing substrate, theweight ratio of the resin to the colorant may be at most 7:1, at most5:1, at most 3:1, at most 2.5:1, at most 2:1, at most 1.7:1, at most1.5:1 at most 1.2:1, at most 1:1, at most 0.75:1, or at most 0.5:1.

Specific resins that may be suitable for use in the inventive inkformulation, system, and process of the present invention includewater-soluble acrylic styrene copolymers within a particular range ofmolecular weights and a low glass transition temperature (T_(g)).Commercial examples of such copolymers may include Joncryl® HPD 296,Joncryl® 142E, Joncryl® 637, Joncryl® 638, and Joncryl® 8004; Neocryl®BT-100, Neocryl® BT-26, Neocryl® BT-9, and Neocryl® BT-102.

Nominally, the resin solution or dispersion may be, or include, anacrylic styrene co-polymer (or co(ethylacrylate metacrylic acid)solution or dispersion. The acrylic styrene co-polymer from the inkformulation ultimately remains in the ink film adhering to the printingsubstrate.

The average molecular weight of the acrylic styrene co-polymer (orco(ethylacrylate metacrylic acid) may be less than 100,000, less than80,000, less than 70,000, less than 60,000, less than 40,000, or lessthan 20,000 g/mole.

The average molecular weight of the acrylic styrene co-polymer may be atleast 10,000, at least 12,000, at least 13,000, or at least 14,000, andin some cases, at least 16,000, or at least 18,000 g/mole.

In one embodiment, the ink film in the ink film constructions accordingto the present invention is devoid or substantially devoid of wax.Typically, the ink film according to the present invention contains lessthan 30% wax, less than 20% wax, less than 15% wax, less than 10% wax,less than 7% wax, less than 5% wax, less than 3% wax, less than 2% wax,or less than 1% wax.

In one embodiment, the ink film according to the present invention isdevoid or substantially devoid of oils such as mineral oils andvegetable oils (e.g., linseed oil and soybean oil), or various oils usedin offset ink formulations. Typically, the ink film according to thepresent invention contains at most 20%, at most 12%, at most 8%, at most5%, at most 3%, at most 1%, at most 0.5%, or at most 0.1%, by weight, ofone or more oils, cross-linked fatty acids, or fatty acid derivativesproduced upon air-drying.

In one embodiment, the ink film according to the present invention isdevoid or substantially devoid of one or more salts, including saltsused to coagulate or precipitate ink on a transfer member or on asubstrate (e.g., calcium chloride). Typically, the ink film according tothe present invention contains at most 8%, at most 5%, at most 4%, atmost 3%, at most 1%, at most 0.5%, at most 0.3%, or at most 0.1% of oneor more salts.

In one embodiment, the ink film according to the present invention isdevoid or substantially devoid of one or more photoinitiators.Typically, the ink film according to the present invention contains atmost 2%, at most 1%, at most 0.5%, at most 0.3%, at most 0.2%, or atmost 0.1% of one or more photoinitiators.

In one embodiment, the printing substrate of the inventive ink filmconstruction is devoid or substantially devoid of one or more solublesalts, including salts used for, or suitable for coagulating orprecipitating ink, or components thereof, on the substrate (e.g.,calcium chloride). In one embodiment, the printing substrate of theinventive ink film construction contains, per 1 m² of paper, at most 100mg of soluble salts, at most 50 mg of soluble salts, or at most 30 mg ofsoluble salts, and more typically, at most 20 mg of soluble salts, atmost 10 mg of soluble salts, at most 5 mg of soluble salts, or at most 2mg of soluble salts.

In one embodiment, the ink film in the ink film constructions accordingto the present invention contains at most 5%, at most 3%, at most 2%, atmost 1%, or at most 0.5%, by weight, of inorganic filler particles suchas silica.

In one embodiment, the dried resins present in the ink film of theinvention may have a solubility of at least 3%, at least 5%, or at least10% in water, at at least one particular temperature within atemperature range of 20° C. to 60° C., at a pH within a range of 8 to 10or within a range of 8 to 11.

In one embodiment, the recovered ink film of the invention may have asolubility of at least 3%, at least 5%, or at least 10% in water, at atleast one particular temperature within a temperature range of 20° C. to60° C., at a pH within a range of 8 to 10 or within a range of 8 to 11.

Waterfastness of Print Images

ASTM Standard F2292-03 (2008), “Standard Practice for Determining theWaterfastness of Images Produced by Ink Jet Printers Utilizing FourDifferent Test Methods—Drip, Spray, Submersion and Rub”, may be used toassess the waterfastness of ink dots and films printed on varioussubstrates. The inventors used three of these test methods: drip, spray,and submersion, to evaluate waterfastness.

In all three tests, the inventive ink film constructions exhibitedcomplete waterfastness; no ink bleeding, smearing or transfer wasobserved.

Identification of Nitrogen-Based Conditioners in a Printed Image on aSubstrate

When, prior to printing, the outer surface of the ITM is pre-treated orconditioned with a chemical agent that is, or contains, at least onenitrogen-based conditioning agent such as a polyethylene imine (PEI),transfer of the printed image to a substrate may typically result in atleast some of the nitrogen-based conditioner being transferred as well.This conditioner may be detected using X-ray photoelectron spectroscopy(XPS) or by other means that will be known to those of ordinary skill inthe art of polymer analysis or chemical analysis of polymers or organicnitrogen-containing species.

In one exemplary demonstration, two printed paper substrates wereprepared under substantially identical conditions (including: inkjettingaqueous inkjet ink having nanopigment particles onto a transfer member;drying the ink on the transfer member; and transferring the ink filmproduced to the particular substrate), except that the first substratewas printed without preconditioning of the transfer member, while forthe second substrate the ITM was conditioned with a polyethylene imine.XPS analysis of the printed images was conducted using a VG ScientificSigma Probe and monochromatic Al Kα x-rays at 1486.6 eV having a beamsize of 400 μm. Survey spectra were recorded with a pass energy of 150eV. For chemical state identification of nitrogen, high energyresolution measurements of N1s were performed with a pass energy of 50eV. The core level binding energies of the different peaks werenormalized by setting the binding energy for the C1s at 285.0 eV.Deconvolution of the observed peaks revealed that the PEI pre-treatedsample contained a unique peak at about 402 eV, which corresponds to aC—NH₂ ⁺—C group.

Thus, in some embodiments of the invention, there is provided a printedink image having an XPS peak at 402.0±0.4 eV, 402.0±0.3 eV, or 402.0±0.2eV.

Inventors have found that at the top or upper surface of the film,distal to the top surface of the substrate, the surface concentration ofnitrogen may appreciably exceed the concentration of nitrogen within thebulk of the film. The concentration of nitrogen within the bulk of thefilm may be measured at a depth of at least 30 nanometers, at least 50nanometers, at least 100 nanometers, at least 200 nanometers, or atleast 300 nanometers below the upper film surface.

In some embodiments, the ratio of the surface nitrogen concentration toa nitrogen concentration within the bulk of the film is at least 1.1:1,at least 1.2:1, at least 1.3:1, at least 1.5:1, at least 1.75:1, atleast 2:1, at least 3:1, or at least 5:1.

In some embodiments, the ratio of nitrogen to carbon (N/C) at the upperfilm surface to a ratio of nitrogen to carbon (N/C) within the bulk ofthe film is at least 1.1:1, at least 1.2:1, at least 1.3:1, at least1.5:1, at least 1.75:1, or at least 2:1.

In some embodiments, the concentration of a secondary amine group at theupper film surface exceeds a concentration of a secondary amine groupwithin the bulk of the film.

In some embodiments, the concentration of a tertiary amine group at theupper film surface exceeds a concentration of a tertiary amine groupwithin the bulk of the film.

In some embodiments, the concentration of secondary and tertiary aminegroups at the upper film surface exceeds a concentration of secondaryand tertiary amine groups within the bulk of the film.

In some embodiments, the upper film surface contains at least one PEI.

In some embodiments, the upper film surface contains at least one polyquaternium cationic guar, such as a guar hydroxypropyltrimoniumchloride, and a hydroxypropyl guar hydroxypropyltrimonium chloride.

In some embodiments, the upper film surface contains a polymer havingquaternary amine groups, such as an HCl salt of various primary amines.

As used herein in the specification and in the claims section thatfollows, the term “colorant” refers to a substance that is considered,or would be considered to be, a colorant in the art of printing.

As used herein in the specification and in the claims section thatfollows, the term “pigment” refers to a finely divided solid coloranthaving an average particle size (D₅₀) of at most 300 nm. Typically, theaverage particle size is within a range of 10 nm to 300 nm. The pigmentmay have an organic and/or inorganic composition. Typically, pigmentsare insoluble in, and essentially physically and chemically unaffectedby, the vehicle or medium in which they are incorporated. Pigments maybe colored, fluorescent, metallic, magnetic, transparent or opaque.

Pigments may alter appearance by selective absorption, interferenceand/or scattering of light. They are usually incorporated by dispersionin a variety of systems and may retain their crystal or particulatenature throughout the pigmentation process.

As used herein in the specification and in the claims section thatfollows, the term “dye” refers to at least one colored substance that issoluble or goes into solution during the application process and impartscolor by selective absorption of light.

As used herein in the specification and in the claims section thatfollows, the term “average particle size”, or “d₅₀”, with reference tothe particle size of pigments, refers to an average particle size, byvolume, as determined by a laser diffraction particle size analyzer(e.g., Mastersizer™ 2000 of Malvern Instruments, England), usingstandard practice.

With regard to fibrous printing substrates, persons skilled in theprinting arts will appreciate that coated papers used for printing maybe generally classified, functionally and/or chemically, into twogroups, coated papers designed for use with non-inkjet printing methods(e.g., offset printing) and coated papers designed specifically for usewith inkjet printing methods employing aqueous inks. As is known in theart, the former type of coated papers utilize mineral fillers not onlyto replace some of the paper fibers in order to reduce costs, but toimpart specific properties to paper, such as improved printability,brightness, opacity, and smoothness. In paper coating, minerals are usedas white pigments to conceal the fiber, thereby improving brightness,whiteness, opacity, and smoothness. Minerals commonly used to this endare kaolin, calcined clay, ground calcium carbonate, precipitatedcalcium carbonate, talc, gypsum, alumina, satin white, blanc fixe, zincsulfide, zinc oxide, and plastic pigment (polystyrene).

Coated papers designed for use in non-inkjet printing methods havehitherto been unsuitable for use with aqueous inkjet inks, or produceprint dots or splotches that may be manifestly different from theprinted ink film constructions of the present invention.

In contrast, specialty coated papers designed for use with inkjet inks,which in some cases may have layer of filler pigment as with other typesof coated papers, may also include a layer of highly porous mineral,usually silica, in combination with a water-soluble polymer such aspolyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP), which acts as abinder, upon which the ink is printed. Such coated inkjet papers aredesigned to quickly remove the water from the printed ink, facilitatingthe printing of ink droplets with good uniformity and edge roughness.The present invention encompasses ink droplets printed on uncoated paperas well as coated paper not designed for inkjet use, but someembodiments of the present invention are not intended to encompass inkdroplets printed on special coated inkjet paper.

Thus, in some embodiments, the substrate is an uncoated paper. In otherembodiments, the substrate is a coated paper that does not contain awater-soluble polymer binder in a layer upon which the ink is printed.

As used herein in the specification and in the claims section thatfollows, the term “commodity coated fibrous printing substrate” is meantto exclude specialty and high-end coated papers, including photographicpaper and coated inkjet papers.

In a typical paper coating of a commodity coated fibrous printingsubstrate, the coating formulation may be prepared by dispersingpigments, such as kaolin clay and calcium carbonate into water, thenadding in binder, such as polystyrene butadiene copolymer and/or anaqueous solution of cooked starch. Other paper coating ingredients, suchas rheological modifiers, biocides, lubricants, antifoaming compounds,crosslinkers, and pH adjusting additives may also be present in smallamounts in the coating.

Examples of pigments that can be used in coating formulations arekaolin, calcium carbonate (chalk), China clay, amorphous silica,silicates, barium sulfate, satin white, aluminum trihydrate, talcum,titanium dioxide and mixtures thereof. Examples of binders are starch,casein, soy protein, polyvinylacetate, styrene butadiene latex, acrylatelatex, vinylacrylic latex, and mixtures thereof. Other ingredients thatmay be present in the paper coating are, for example, dispersants suchas polyacrylates, lubricants such as stearic acid salts, preservatives,antifoam agents that can be either oil based, such as dispersed silicain hydrocarbon oil, or water-based such as hexalene glycol, pH adjustingagents such as sodium hydroxide, rheology modifiers such as sodiumalginates, carboxymethylcellulose, starch, protein, high viscosityhydroxyethylcellulose, and alkali-soluble lattices.

As used herein in the specification and in the claims section thatfollows, the term “fibrous printing substrate” of the present inventionis specifically meant to include:

-   -   Newsprint papers including standard newsprint, telephone        directory paper, machine-finished paper, and super-calendered        paper;    -   Coated mechanical papers including light-weight coated paper,        medium-weight coated paper, high-weight coated paper, machine        finished coated papers, film coated offset;    -   Woodfree uncoated papers including offset papers, lightweight        papers;    -   Woodfree coated papers including standard coated fine papers,        low coat weight papers, art papers;    -   Special fine papers including copy papers, digital printing        papers, continuous stationery;    -   Paperboards and Cartonboards; and    -   Containerboards.

As used herein in the specification and in the claims section thatfollows, the term “fibrous printing substrate” of the present inventionis specifically meant to include all five types of fibrous offsetsubstrates described in ISO 12647-2.

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

It will be appreciated that certain features of the invention, whichare, for clarity, described in the context of separate embodiments, mayalso be provided in combination in a single embodiment. Conversely,various features of the invention, which are, for brevity, described inthe context of a single embodiment, may also be provided separately orin any suitable sub-combination.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims. All publications, patents and patentapplications mentioned in this specification, including the appendices,are hereby incorporated in their entirety by reference into thespecification, to the same extent as if each individual publication,patent or patent application was specifically and individually indicatedto be incorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention.

What is claimed is:
 1. An ink film construction comprising: (a) a firstprinting substrate selected from the group consisting of an uncoatedfibrous printing substrate, a commodity coated fibrous printingsubstrate, and a plastic printing substrate; and (b) an ink dot setcontained within a square geometric projection projecting on said firstprinting substrate, said ink dot set containing at least 10 distinct inkdots, fixedly adhered to a surface of said first printing substrate, allsaid ink dots within said square geometric projection being counted asindividual members of said set, each of said ink dots containing atleast one colorant dispersed in an organic polymeric resin, each of saiddots having an average thickness of less than 2,000 nm, and a diameterof 5 to 300 micrometers; each ink dot of said ink dots having agenerally convex shape in which a deviation from convexity, (DC_(dot)),is defined by:DC _(dot)=1−AA/CSA, AA being a calculated projected area of said dot,said area disposed generally parallel to said first fibrous printingsubstrate; and CSA being a surface area of a convex shape that minimallybounds a contour of said projected area; wherein a mean deviation fromconvexity (DC_(dotmean)) of said ink dot set is at most 0.05.
 2. The inkfilm construction of claim 1, said mean deviation being at most 0.04, atmost 0.03, at most 0.025, at most 0.022, at most 0.02, at most 0.018, atmost 0.017, at most 0.016, at most 0.015, or at most 0.014.
 3. The inkfilm construction of claim 1, said square geometric projection having aside length within a range of 0.5 mm to 15 mm.
 4. The ink filmconstruction of claim 1, said square geometric projection having a sidelength of about 10 mm, 5 mm, 2 mm, 1 mm, 0.8 mm, or 0.6 mm.
 5. The inkfilm construction of claim 1, said diameter being at least 7, at least10, at least 12, at least 15, at least 18, or at least 20 micrometers.6. The ink film construction of claim 1, wherein said first printingsubstrate is an uncoated fibrous printing substrate.
 7. The ink filmconstruction of claim 1, wherein said first printing substrate is acommodity coated fibrous printing substrate.
 8. The ink filmconstruction of claim 7, said mean deviation being at most 0.013, atmost 0.012, at most 0.010, at most 0.009, or at most 0.008.
 9. The inkfilm construction of claim 1, wherein said first printing substrate is aplastic printing substrate.
 10. The ink film construction of claim 9,said mean deviation being at most 0.013, at most 0.012, at most 0.010,at most 0.009, or at most 0.008.
 11. The ink film construction of claim9, said plurality of ink dots exhibiting, on said plastic printingsubstrate, an adhesive failure of at most 10%, or at most 5%, whensubjected to a standard tape test.
 12. The ink film construction ofclaim 9, said plurality of ink dots being substantially free of adhesivefailure when subjected to a standard tape test.
 13. The ink filmconstruction of claim 1, said ink dot set having at least 20, at least50, or at least 200 of said distinct ink dots.
 14. The ink filmconstruction of claim 1, said DC_(dotmean) being at least 0.0005, atleast 0.001, at least 0.0015, at least 0.002, at least 0.0025, at least0.003, at least 0.004, at least 0.005, at least 0.006, at least 0.008,at least 0.010, at least 0.012, or at least 0.013.
 15. The ink filmconstruction of claim 1, said average thickness being within a range of100-1,200 nm, 200-1,200 nm, 200-1,000 nm, 100-800 nm, 100-600 nm,100-500 nm, 100-450 nm, 100-400 nm, 100-350 nm, 100-300 nm, 200-450 nm,200-400 nm, or 200-350 nm.
 16. The ink film construction of claim 1,said average thickness being at most 1,800 nm, at most 1,500 nm, at most1,200 nm, at most 1,000 nm, at most 800 nm, at most 500 nm, at most 450nm, or at most 400 nm.
 17. An ink film construction comprising: (a) afirst printing substrate selected from the group consisting of anuncoated fibrous printing substrate, a commodity coated fibrous printingsubstrate, and a plastic printing substrate; and (b) an ink dot setcontained within a square geometric projection projecting on said firstprinting substrate, said ink dot set containing at least 10 distinct inkdots, fixedly adhered to a surface of said first printing substrate, allsaid ink dots within said square geometric projection being counted asindividual members of said set, each of said ink dots containing atleast one colorant dispersed in an organic polymeric resin, each of saiddots having an average thickness of less than 2,000 nm, and a diameterof 5 to 300 micrometers; each ink dot of said ink dots having adeviation from a smooth circular shape, (DR_(dot)), represented by:DR _(dot) =[P ²/(4π·A)]−1, P being a measured or calculated perimeter ofsaid ink dot; A being a maximal measured or calculated area contained bysaid perimeter; wherein a mean deviation (DR_(dotmean)) of said ink dotset is at most 0.60.
 18. An ink film construction according to claim 1,wherein a plurality of said ink dots form a continuous ink film coveringan area of said surface, said film having an average thickness of atmost 2,200 nm, at most 2,100 nm, at most 2,000 nm, at most 1,900 nm, atmost 1,800 nm, at most 1,700 nm, at most 1,600 nm, at most 1,500 nm, orat most 1,400 nm; wherein, within said area, the ink film constructionexhibits a color gamut volume of at least 425 kilo(ΔE)³, at least 440kilo(ΔE)³, at least 460 kilo(ΔE)³, at least 480 kilo(ΔE)³, or at least500 kilo(ΔE)³.
 19. The ink film construction of claim 18, wherein saidprinting substrate is a fibrous printing substrate.
 20. An ink filmconstruction according to claim 17, wherein a plurality of said ink dotsform a continuous ink film covering an area of said surface, said filmhaving an average thickness of at most 2,200 nm, at most 2,100 nm, atmost 2,000 nm, at most 1,900 nm, at most 1,800 nm, at most 1,700 nm, atmost 1,600 nm, at most 1,500 nm, or at most 1,400 nm; within said area,the ink film construction exhibits a color gamut volume of at least 425kilo(ΔE)³, at least 440 kilo(ΔE)³, at least 460 kilo(ΔE)³, at least 480kilo(ΔE)³, or at least 500 kilo(ΔE)³.